Regarding this issue, Marxist philosophy believes that it is possible for one to know the world, and that the human mind is capable of discovering objective realities. [In other words], it rejects doubt and sophistry.

In contrast to idealism which denies the possibility of knowing the world and its laws, which sees no value to our knowledge, which does not admit objective reality, and which believes that the world is full of things subsisting by themselves and which science will never get to know, the Marxist philosophical materialism rests on the principle which states that it is possible to have exact knowledge of the world and of its laws. Our knowledge of the natural laws, which is the knowledge achieved by practice and sense experience, is valuable and signifies objective reality. The world does not contain anything that cannot be known. Rather, it contains certain things that are still (p. 108) unknown, but that will be discovered, and will become known by means of the scientific and practical methods. [1]

Again:

The strongest refutation of this philosophical illusion, i.e. the illusion of Kant, Hume and other idealists, as well as of every other philosophical illusion is practice, sense experience and industry in particular. Thus, if we can prove that we comprehend accurately a natural phenomenon, i.e. a phenomenon which we have not created ourselves, or made it occur by means of fulfilling its conditions in themselves; and further still, if we can employ this phenomenon in achieving our goals; then this would be a decisive blow to the Kantian notion of the thing in itself which is inaccessible to knowledge. [2]

These declarations show clearly that Marxist philosophy was not satisfied with taking the side of sophistry and the schools of denial or skepticism that declared their bankruptcy in the philosophical field. This is because the edifice that Marxism wished to erect must be based on absolute philosophical principles and decisive rules of thought. Unless the principles are certain, then the intellectual edifice that is based on them, cannot be solid and firm.

Now, we would like to try to know whether it is appropriate for this kind of philosophy to claim for itself philosophical certainty, and to claim further that decisive knowledge is possible. In other words, can Marxist philosophy, whose method of thought is along dialectical lines, assert a true knowledge of the world and its laws, and free itself from the grip of skepticism and sophistry? Put differently, is the philosophy in which the Marxist philosopher rejoices of a higher value and a superior character than knowledge in the philosophy of Kant, (p. 109) the idealists, and the relative materialists who were among the philosophers of the schools of skepticism that were criticized and attacked by Marxism?

In order for us to understand the problem, to find out whether it is possible to solve it on the basis of Marxist philosophy, and to understand the point of view of Islamic philosophy concerning it, we must mention briefly the most important philosophical doctrines that dealt with it, in order that the following will be clearly determined: the position of Marxism regarding this problem, the kind of view that Marxism must adopt in accordance with its main principles, and the analysis and scrutiny that this problem merits.

The Views of the Greeks

In the fifth century B.C., a wave of sophistry pervaded Greek thought at a time in which the method of disputation spread in the fields of rhetoric and law, and philosophical views and non-empirical assumptions strongly clashed. Philosophical thought had not yet crystallized, nor had it reached a high degree of intellectual maturity. Thus, such a conflict and clash among the contradictory philosophical views were the cause of .intellectual confusion and deep fear. The habit of disputation nourished that situation by means of ambiguities and invalid syllogisms which it provided to its disputant heroes. On the basis of such ambiguities and invalid syllogisms, these heroes denied the world by rejecting all the human intellectual principles as well as the sensible and intuitive propositions.

Gorgias, [35] one of the prominent leaders of this school, wrote a book on non-existence. In this work, he tried to prove a number of points: (1) nothing exists; (2) if anything exists, one cannot know it; (8) if we assume that one can know it, one cannot communicate it to others. (p. 110)

For quite a while, sophistry had expressed in various ways its disregard for philosophy and science, until Socrates, Plato and Aristotle emerged and held strong positions against it. Aristotle laid down his well-known logic for discovering the sophistical fallacies and for organizing human thought. His epistemological doctrine may be summarized as follows.

Sense knowledge and primary or secondary rational knowledge, which are acquired by taking into consideration logical principles, are truths with an absolute value. Due to this, Aristotle permits in demonstration (the absolute evidence in his logical sense) the use of both sense knowledge and rational knowledge.

Later, an attempt was made to reconcile the two opposite tendencies - that is, the tendency leaning toward absolute denial (sophistry), and the tendency asserting affirmation (Aristotelian logic). This attempt was represented in the skeptical doctrine thought to have been founded by Pyrrho [36] who is known for his ten proofs for the necessity of absolute doubt. According to Pyrrho, every proposition can be stated in one of two ways: it can be either affirmed or denied with equal force.

But the doctrine of certitude finally prevailed in the philosophical field, and reason mounted the throne given to it by Aristotle, judging and making decisions while bound by the logical criteria. The fire of doubt died down for centuries, until around the sixteenth century when the natural sciences became active and made discoveries of unexpected truths, especially in astronomy and the general order of the universe. These scientific developments were similar to the force of disputation in the Greek period. Thus, they revived the doctrines of doubt and denial which resumed their activities with various methods. A conflict arose among the upholders of certitude themselves concerning the limits of certainty on which human beings must depend. (p.111)

Descartes emerged in this atmosphere, which was saturated with the spirit of doubt and rebellion against the authority of mind. He presented the world with a philosophy of certitude that had a great influence on bringing back some degree of certitude to the philosophical tendency.

Descartes

Descartes is one of the prominent rationalists, and one of the founders of the philosophical renaissance in Europe. He began his philosophy with sweeping and stormy doubt. [He reasoned that] because ideas are incompatible, they are, therefore, susceptible to error. Sense perception, too, is often deceptive; therefore, it must also be discounted. With these two considerations, the wave of doubt raged, rooting out the material and the spiritual worlds, since the way to both of these worlds is through ideas and sense perception.

Descartes insists on the necessity of this absolute doubt. He demonstrates its logic by the fact that it is possible for a human being to be at the merry of a power that takes hold of his existence and mind, and that attempts to deceive and mislead him. Thus, it inspires him with ideas that do not correspond to reality, and with false perceptions. Regardless of the clarity of such ideas and perceptions, we cannot discount this assumption, which requires us to take doubt as a perpetual doctrine.

However, Descartes excludes one truth which stands firm in the face of the storm and is unshaken by the tendencies of doubt - this truth being his thought, which is an indubitable, actual reality. Doubt does not affect it, except perhaps by strengthening its stability and clarity; for doubt is nothing but a kind of thought. Even if that deceptive power were to exist, it could not deceive us with regard to our conviction about this thought. The reason is that it would have to deceive us by way of inspiring us with false ideas. This means that thought is a fixed truth in (p. 112) any case; that is, whether the issue of human thought is one of deception and misguidance, or one of understanding and determination.

This truth, then, is the cornerstone of Descartes' philosophy, and the point of departure for philosophical certitude. By means of this truth, Descartes tried to move from conception to existence, and from subjectivity to objectivity. Indeed, by means of it, he tried to prove both the subject and the object. Thus, he began with himself. He demonstrated his existence by this truth, saying: 'I think, therefore, I exist.' [37]

One may notice that this Cartesian proof contains an unconscious acceptance of truths that, for Descartes, are still subject to doubt. This proof is a non-technical expression of the first figure of the syllogism in Aristotelian logic. Technically, it takes the following form: 'I think, every thinker exists, therefore I exist.' In order for this Cartesian reasoning to be valid, Descartes must accept logic, and believe that the first figure of the syllogism yields a conclusion and that its conclusion is true, even though he is still at the beginning of the first stage, and doubt in his mind is still in control of all knowledge and truths, including logic and its rules.

We must warn against the fact that when Descartes began the demonstrative stage of his thought by 'I think, therefore, I exist', he had not felt the need for accepting the syllogistic figures in logic. Rather, he believed that knowledge of his existence by way of his thought is an intuitive matter that does not require the construction of syllogistic figures and the acceptance of their minor and major premises.

Since the proposition, 'I think, therefore, I exist', is true because it is intuitive, such that it is not subject to doubt, anything of the same degree of intuitiveness is also true. With this, Descartes added another proposition to the first intuitive proposition, and admitted as true that a thing does not come out of nothing. (p. 113)

After he accepted the subjective side, he went on to prove the objective reality. Thus, he arranged human thought in three groups:

1. Instinctive or natural ideas. These are the natural human ideas that appear most evident and clearest, such as the ideas of God, motion, extension, and the soul.

2. Vague ideas that occur in the mind on the occasion of motions that come to the senses from without. These have no foundation in the human mind.

3. Various ideas that human beings construct and compose from their other ideas. These are exemplified in the idea of a human being having two heads.

Descartes began by addressing the idea of God in the first group. He decided that it is an idea having an objective reality, since in its objective reality, it is superior to the human thinker and all his ideas. This is because the human thinker is deficient and limited; while the idea of God is the idea of a being absolutely perfect and infinite. Because Descartes had already accepted the view that a thing does not come out of nothing, he knew that there is a cause of this natural concept in his mind. He himself cannot be the cause of it, since it is more sublime and complete than he is. A thing cannot be more sublime than its cause; otherwise, increase [in the value of the] caused object would come out of nothing. Thus, the idea of God must have proceeded from an infinite being whose perfection and greatness are equal to its own. This being is the first external objective reality that Cartesian philosophy admits - this reality being God.

By means of this absolutely perfect being, Descartes proved that every natural thought in the human nature is true and reflects an objective reality. This is because the rational ideas in the first group proceed from God. Thus, if they are not true, (p. 114) then their being given by God to human beings would be deceptive and dishonest. But this is impossible in the case of a being who is absolutely perfect.

Because of this, Descartes accepted the human innate or rational knowledge and the fact that it is valid and true. He accepted the innate ideas only, to the exclusion of any other ideas that proceed from external causes. As a result of this, he divided ideas concerning matter into two types: (1) the innate ideas, such as the idea of extension; and (2) ideas that occur [later] and express specific reactions of the soul, caused by external influences, such as the ideas of sound, odor, light, flavor, heat and color. The former are real primary qualities, while the latter are secondary qualities that do not express objective realities. Rather, they represent subjective reactions. They are successive mental concepts that arise in the mental realm due to the influence of external bodies to which they have no resemblance.

This is a very brief presentation of the Cartesian theory of knowledge. To begin with, we must know that the fundamental principle on which Descartes based his doctrine and philosophical certitude, 'I think, therefore, I exist', was criticized in Islamic philosophy a few centuries prior to Descartes' time. Ash-Shaykh ar-Ra'is, Ibn Sina, [38] presented it and criticized it as being unfit as a method of scientific evidence for the existence of the human thinker himself. A human being cannot prove his existence by means of his thought. This is so, because if by saying, 'I think, therefore, l exist', he wishes to prove his existence by means of his specific thought only, then he proves his specific existence at the outset and admits his existence in the very first phrase. If, on the other hand, he (p. 115) wishes to make the absolute thought as an evidence of his existence, he is at fault, because an absolute thought asserts the existence of an absolute thinker, not a specific thinker. Thus, the specific existence of every thinker must be known to him in a primary manner, regardless of any considerations, including his doubt and his thought.

Subsequently, we find Descartes erecting the whole edifice of existence on one point - namely, that the ideas which God created in human beings signify objective realities. If they did not do so properly, God would be a deceiver. But it is impossible for God to deceive.

It is easy to see in Descartes' proof the confusion between reflective knowledge and practical knowledge. The proposition, 'Deception is impossible', is an unfaithful translation of the proposition, 'Deception is abominable'. But this latter proposition is not a philosophical proposition. Rather, it is a practical idea. How, then, did Descartes doubt everything, without doubting this practical knowledge on which he based the philosophical reflective knowledge? In addition, the succession of knowledge plays a clear role in the Cartesian doctrine. When he accepted the theological position, he based his acceptance on a proposition whose truth is accepted a priori: 'A thing does not come out of nothing.' But this proposition in turn requires an affirmation of the theological position, in order to secure its truth. Unless it is shown that human beings are ruled by an undeceptive, wise power, it is not permissible for Descartes to accept this proposition and terminate his doubt concerning a deceptive power in control of the human mind.

Finally, there is no need for us to point out another confusion that Descartes made between the idea of God and the objective reality that this idea signifies, when he asserts that it is impossible for this idea to proceed from human beings, since it is more sublime than they are. The truth is that this idea is not more sublime than human minds. Rather, it is impossible for human beings to create the objective reality of this idea (p. 116)

Actually, our purpose is not to elaborate the discussion on Descartes. Rather, we intend to present his point of view regarding the value of human knowledge, a view that may be summed up in the acceptance of the absolute value of rational knowledge, especially innate knowledge.

John Locke

Locke is a primary representative of the empirical or experiential theory, as we learned earlier. His view concerning the theory of knowledge is that knowledge is divided into the following types:

1. Intuitive knowledge (al-ma'rifa al-wijdaniyya): this is the knowledge the mind can attain without need for recognizing something else. An example of this is our knowledge that one is half of two.

2. Reflective knowledge (al-ma'rifa at-ta' ammuliyya): this kind of knowledge cannot occur without the help of previous information. An example of it is our knowledge that the sum of the angles of a triangle is equal to two right angles.

3. Knowledge that results from empirical knowledge of the known object.

Locke believes that intuitive knowledge is real knowledge, having complete philosophical value. The same is true of the reflective knowledge that can be clarified as valid reasoning. As for empirical knowledge, it has no philosophical value, even though it is taken into the consideration of the standard of practical life. Due to this, Locke does not accept the objectivity of all of the qualities of matter that are known by the senses. Rather, he considers some of them real and objective, such as form, extension and motion, and some others subjective reactions, such as color, flavor, odor and other similar qualities.

This very Lockean theory of knowledge and its philosophical weight are not in agreement with Locke's own view of the analysis of knowledge. For all knowledge, according to him, is derived (p. 117) from the senses and sense experience. Even intuitive knowledge, such as the principle of noncontradiction and other similar primary principles in the human mind, is not possessed by human beings except in this way. The senses, the primary source of this knowledge, do not have an absolute philosophical value in Locke's theory of knowledge. The natural conclusion to this is the absolute doubt concerning the value of any human knowledge, since in its essence and primary reality, knowledge is nothing but a sense perception acquired by external or internal experience.

Thus, it seems that Locke's division of knowledge into three groups, and his distinction among these groups from a philosophical point of view, are contradictory to the principles that he established. Similarly, his division of the qualities of sensible bodies, which is analogous to the Cartesian division, is not logically consistent with his principles, even though it may be somewhat logically consistent with Descartes' principles. This is because Descartes divides knowledge into rational knowledge and empirical knowledge, and accepts the former philosophically, but not the latter. He claims that people's ideas concerning some bodily qualities are among the innate rational ideas, while their ideas concerning some other bodily qualities are empirical. Due to this, it was possible for him to divide these qualities into primary and secondary, and to assert that the primary qualities are real and objective, while the secondary qualities are not.

As for John Locke, he began his philosophical endeavor by eliminating the innate ideas, and asserting the mastery of the senses over all knowledge. Thus, there is no way of knowing the bodily qualities except through the senses. What, then, is the philosophical difference between some of these qualities and some others?

The Idealists

Idealist doctrine has deep roots in the history of human thought, and is of various forms. The term 'idealism' is one of the terms that played an important role in (p. 118) the history of philosophy. It exchanged a number of philosophical notions in which it crystallized. Due to this, it acquired a kind of vagueness and confusion.

Idealism played its first role in the philosophical tradition at the hands of Plato, who offered a specific theory of human reason and knowledge. This theory was called 'the theory of Platonic forms'. Plato was an idealist; however, his idealism does not mean a denial of sensible realities, or a stripping of empirical knowledge from the objective realities that are independent of the realm of conception and knowledge. Rather, he affirmed the objectivity of sense perception. He went further than this to affirm the objectivity of rational knowledge, which is superior to empirical knowledge, asserting that rational knowledge -that is, knowledge of general types, such as knowledge of the ideas of 'human being', 'water', and 'light', have an objective reality independent of intellection, as was pointed out in the first part of this investigation.

Thus, we learn that ancient idealism was a form of excessive acceptance of objective reality. This is because it accepted the objective reality of sense perception - namely, the knowledge of ideas pertaining to the senses - and of rational knowledge -that is, the knowledge of ideas in general. It did not involve any denial or doubt of reality.

In modern history, idealism took on a meaning completely different from the above-mentioned one. While Platonic idealism emphasized the objective reality of both rational and empirical knowledge, idealism in its modern form was an attempt to shake the foundation of objective reality and declare a new doctrine concerning the theory of human knowledge, by means of which it can eliminate the philosophical value of knowledge. Our concern in the present investigation is to explore and study this new notion of idealism.

This notion was cast in various forms and shapes. (p. 119) Some writers of philosophy went as far as to consider idealism as a description of any philosophy that rests on doubt, that involves an attempt to remove the objective aspect of things from the realm of human knowledge, or that asserts a metaphysical principle of the world. Thus, spiritualism, agnosticism, empiricism, rationalism, criticism and existential phenomenalism are all idealistic philosophies, according to such writers. [3]

In order to clarify the role of idealism in the theory of human knowledge, we will study the important tendencies of modern idealism. These are: (1) the philosophical tendency; (2) the physical tendency; and (3) the physiological tendency.

This form of idealism was founded by Berkeley, who is considered the leader of modern idealism. Berkeley's philosophy is viewed as the point of departure for the idealistic tendency or the conceptual bent in the recent centuries of philosophy.

The essence of idealism in Berkeley's doctrine can be recapitulated in his well-known phrase: 'To exist is to know or to be known.' [39] In other words, it is not possible to assert the existence of a thing, unless that thing knows or is known. The thing that knows is the soul; and the known things are the conceptions and the ideas that subsist in the sphere of sense perception and knowledge. Thus, it is necessary that we accept the existence of the soul and the existence of these ideas. As for the things that are independent of the sphere of knowledge - that is, the objective things - they are non-existent because they are not known.

Following this, Berkeley takes up for discussion the bodies that philosophers call (p. 120) 'material substances' in order to eliminate them from the realm of existence. He says that we do not grasp anything about matter that [philosophers] suppose except a group of mental conceptions and sensible phenomena, such as color, taste, shape, odor and other similar qualities.

Berkeley pursues his idealistic notion of the world, saying that he is not a sophist or a skeptic about the existence of the world and its realities and beings. Rather, he admits that, from a philosophical point of view, al! of this exists, and that in this he does not differ from other philosophers. He differs from them only in the definition of the notion of existence. 'Existence', according to him, does not have the same meaning that it has for others. What exists to others also exists to Berkeley, but according to his own way of interpreting 'existence'. This means that the existence of a thing is nothing but its existence in our knowledge of that thing.

Later, Berkeley asked himself this question: 'If matter does not exist, then from where can we get the sensations that flow in us at every moment, without the influence of our personal will over their flow and succession?' Berkeley had the answer ready: God Himself causes these sensations in us. Thus Berkeley ends his philosophical endeavor by retaining for himself two realities in addition to knowledge. One of these realities is the mind, the knowing subject; and the other is God, the reality that creates our sensations.

This theory completely eliminates the issue of human knowledge and the objective study of the value of knowledge; for this theory does not admit the objectivity of thought and knowledge, or the existence of anything outside their limits. (p. 121)

Berkeley's idealistic notion suffers from some vagueness, which makes it possible to interpret this notion in a number of senses differing in the degree of idealism and depth of the conceptual bent. [Of these] we will take up the most idealistic sense - namely, the pure idealistic sense that does not admit anything except the existence of the knowing soul and the successive sense perceptions and knowledge in the soul. This sense is the best-known among his philosophical statements and is consistent with the proofs by means of which he tried to demonstrate his idealistic notion. The proofs for this notion can be summarized as follows.

The first proof is that all human knowledge is based on, and comes from, the senses. Thus, the senses are the primary principle of knowledge. If we attempt to examine this principle, we find it charged with contradictions and errors. For example, the sense of sight is always [self]-contradictory with respect to its vision of bodies close up and at a distance. It perceives them as small in size when they are remote from it; while it perceives them as large when they are in its proximity. Similarly, the sense of touch is also [self]-contradictory Thus, by means of it, we may have two different pieces of knowledge about the same thing. For the sake of clarification, Berkeley adds: immerse your hands in warm water, after you have immersed one of them in hot water, and the other in cold water. Would not the water appear cold to the hot hand, and hot to the cold hand? But should we then say that the water is hot and cold at the same time? Would not these words be fully nonsensical? Therefore, you must conclude with me that water in itself does not exist as a matter independent of our existence. It is nothing but a name that we give to our sense perceptions. Therefore, water exists in us. In short, matter is the idea that we posit about matter. If sense perceptions are empty of any objective reality pertaining to the contradictories recognized in them, then there will be no objective value of human knowledge at all; for knowledge in general would rest on the senses. If the basis collapses, then the whole pyramid collapses. (p. 122)

But this proof has no value for the following reasons. First, not all human knowledge rests on the senses and sense experience. For rational doctrine, which we studied in an earlier chapter of the investigation, 'the primary source of knowledge determines the presence of necessary primary knowledge in the human mind. Such necessary knowledge does not arise from the senses, and no contradiction at all appears in it. One cannot root out such knowledge by the emotions that affect the senses and the sense knowledge. As long as we possess knowledge free from the influence of emotions, it will be easy to establish a sound objective knowledge on the basis of it.

Second, this proof contradicts the philosophical principle of Berkeley's idealism -that is, the empirical theory and the empirical doctrine. For in this proof, Berkeley considers the principle of non-contradiction as a fixed truth and, from the very beginning, finds improbable the possibility of contradiction in objective reality. On the basis of this, he concludes from the contradictory knowledge and sense experience that they are empty of objective reality. It escapes him that the principle of non-contradiction in empirical doctrine is nothing but an empirical principle demonstrated by sense experience. Thus, if knowledge and sense experience are contradictory, then how is it possible for Berkeley to accept the principle of non-contradiction and demonstrate by means of it the non-existence of objective reality? Further, why is it that, according to him, there cannot exist an objective reality in which phenomena and things contradict one another? The truth is that Berkeley unconsciously relied on his nature that asserts the principle of non-contradiction as independent of the senses and sense experience.

Third, it is necessary that we distinguish between two issues, one of which is the issue of the existence of the objective reality of knowledge and sense perception; and the other is the issue of the correspondence of this reality to what appears to us in our knowledge and sense perception. If we distinguish between these two issues, we will be able to know that the contradiction of sense perception cannot be taken as a proof of the non-existence (p. 128) of an objective reality, as Berkeley thought. Rather, it indicates a non-agreement between the idea known by the senses and the external objective reality. This is to say that sense perception need not fully agree with external things. But this is different from Berkeley's attempt to deny the objectivity of sense perception. When we immerse our hands in water and one of them feels hot, while the other feels cold, we are not required, for the purpose of eliminating contradiction, to deny the objectivity of sense perception absolutely. Rather, we can explain the contradiction in a different way namely, that our sense perceptions are nothing but psychological reactions to external things. Thus, there must be an external thing if we are to have a sense perception or if we are to have a reaction. But it is not necessary that the sense perception agree with the objective reality; for, since sense perception is a subjective reaction, it is not separate from the subjective aspect. On the basis of this, we can immediately judge that the water that Berkeley supposes to be warm and not to be hot or cold is the objective reality that causes in us the two contradictory sense perceptions, and that the two sense perceptions contradict one another due to the subjective aspect that we add to things when we know them or when we have reactions to them.

The second proof is that the acceptance of the existence of things outside our souls and conceptions rests on the fact that we see and touch such things; that is, that we believe they exist because they provide us with certain sense perceptions. However, our sense perceptions are nothing but ideas contained in our souls. Therefore, the things that our senses know are nothing but ideas, and ideas cannot exist outside our souls.

In this proof, Berkeley attempts to make the issue of accepting the objective reality of things dependent on direct conjunction with that reality. As long as it is not possible for us under any circumstances to have direct conjunction with things external to our souls, and as long as we are necessitated to know such things in our private conceptions and ideas, (p. 124) then in truth, there is no existence except for these conceptions and ideas. If we destroy such conceptions and ideas, there will be nothing left that we can know or whose existence we can admit.

To begin with, we must notice that this argument, by means of which Berkeley attempts to demonstrate his idealistic notion, is unsound, even according to Berkeley himself. For he agrees with us, though unconsciously, that it is untenable and insufficient for justifying the idealistic notion. This is because it leads to subjective idealism that denies the existence of other individuals, as well as the existence of nature. If reality is limited to knowledge and consciousness themselves because we have no conjunction with anything beyond the limits of the mind and its conscious contents, then such knowledge and consciousness will be my knowledge and my consciousness. I will have no conjunction with the knowledge and consciousness of others, as I will have no conjunction with nature itself. This will impose on me isolation from everything, other than my existence and my mind. Thus, it will not be appropriate for me to accept the existence of other human beings, since they are nothing but the conceptions of my mind and subjective thoughts. Therefore, this inquiry leads to an incredible individualistic idealism. Is it then possible for Berkeley to be driven to adopt an extreme form of his argument and draw from it this kind of idealism? Had he tried something like this, he would have contradicted himself before contradicting others. [If we are wrong], then with whom did he converse, for whom did he write and compose, and for whose sake did he lecture and teach? Is this not a firm assertion by Berkeley of the objective reality of other individuals? Thus, it becomes clear that Berkeley himself shares with us the non-acceptance of the argument that he had adopted, and the acceptance, though unconsciously, of its falsehood.

Now, it remains for us to clarify the secret behind the fallacy in this proof, in order to understand why people, including Berkeley himself, cannot attain actual conviction concerning it. In this regard, we must remember what we learned in the first part of (p. 125) the investigation, 'the primary source of knowledge' - namely, that human knowledge is divided into two main divisions: assent and conception. We must also know the basic quality that distinguishes assent from conception. This quality is what makes knowledge of the assent type a link between us and the external world.

To put this more clearly, conception is nothing but the presence of the form of one of the essences in our specific intellective faculties. The form may be present in our senses. This sort of presence constitutes the sense perception of this form. Again, the form may be present in our imaginative faculty. By means of this presence, imagination occurs. Further, the form may be present in the mind in its general abstract nature. This kind of presence is called 'intellection'. Thus, sense perception, imagination and intellection are various kinds of conception, and different ways in which the forms of things are present in the human intellective faculties. We conceive the apple on the tree by perceiving it through vision. Our sense perception of it means that its form is present in our senses. Later, we retain this form in our mind after we depart from the tree. This latter type of presence is imagination. After this, we can eliminate from this form the qualities that distinguish it, from other apples, retaining only its general idea -that is, the universal idea of apple. This universal form is intellection.

These are the three stages of conception that human, knowledge crosses. Every one of these stages is just the presence of a form in some of our intellective faculties. Therefore, conception, on the whole, is no more than the presence in our intellective faculties of the form of a certain thing, be that a clear and evident conception, such as sense perception, or dull and faint, such as imagining and intellecting. Because of this, conception cannot pave the way for us to reach beyond the form that we conceive in our intellective faculties, nor does it ensure the movement from the subjective realm to the objective realm. The reason for this is that the presence of the form of an essence in our intellective faculty is one thing, while the objective and independent presence of that essence in the outside is something else. Due to this, sense perception may make us conceive numerous things that we do not believe to have any independent objective reality. (p. 126) For example, we conceive a stick immersed in water as broken; yet we know that that stick is not actually broken in water. But we perceive it as such due to the refraction of the light rays in water. Also, we perceive the warm water as very hot, if we immerse our hands in it when they are very cold, even though we are convinced that the heat that we perceive is not objectively real.

Regarding assent - that is, the other type of human knowledge - it is the proper point of our departure from conception to objectivity. Let us, therefore, notice how this is accomplished.

Knowledge of the assent type is nothing but a judgement by the soul that there is a certain reality beyond conception. This is exemplified in our saying, 'A straight line is the shortest distance between two points'. This judgement means that we assert that there is a reality beyond our conception of straight lines, points and distances. That is why it is completely different from the various kinds of pure conception.

First, this judgement is not a form of a specific essence that we can perceive and conceive. Rather, it is a psychological act that links forms. Because of this, it is impossible that it arises in the mind by way of the senses. Rather, it is one of the internal acts of the knowing soul.

Second, this judgement has a subjective property not present in any kind of division of conception. This is the property of revealing a reality beyond the limits of knowledge. For this reason, it is possible that you can conceive or be aware of a thing without, at the same time, believing that it has a reality beyond knowledge and consciousness. However, it is not possible that you have knowledge of the assent type - namely, that you believe that a straight line is the shortest distance between two points, while at the same time doubting the existence of the objective reality of which your knowledge and consciousness speak. (p. 127)

This makes it clear that knowledge of the assent type is the only thing capable of refuting Berkeley's argument which states that we do not have direct conjunction with reality, but that instead we have conjunction with our ideas. Thus, there is no existence for anything except for our own ideas. However, even though the soul has no direct conjunction with anything except with its knowledge, nevertheless, there is a kind of knowledge which by nature has essential disclosure (kashfan dhatiyyan) of a thing that lies outside knowledge. This is the judgement - that is, knowledge of the assent type. Berkeley's argument is based on his confusion between conception and assent, and on his ignorance of the basic differences between the two.

In light of this, it is evident that the empirical doctrine and the empirical theory lead to the idealistic tendency. Both are necessitated to accept the argument offered by Berkeley. This is because, in accordance with these two principles, the human soul does not at all possess either necessary or natural knowledge. Rather, all its knowledge arises from sense perception, and its various kinds of cognition are based on this kind of perception - sense perception being but a form of conception. Thus, regardless of the multiplicity and variety of sense perception, it does not extend beyond its conceptual limits, as it is impossible for human beings to use it to move one step in the direction of objectivity.

The third proof is that if human knowledge and cognition are characterized by essential disclosure of the realm that lies beyond their limits, then all knowledge and cognition must be true. This is because by nature and essence, it is revelatory; and a thing cannot be free from its essential attributes. This is so, in spite of the fact that all human thinkers admit that much of the information and many of the judgements that people have are false and do not disclose anything about reality. Scholars may agree to accept a certain theory, yet later, this theory is shown to be clearly false. How can this be understood in light of the claims made by realistic philosophy - namely, that knowledge enjoys essential disclosure? Is there any way out for this philosophy other than to concede that knowledge does not enjoy such a quality? (p. 128) But if it concedes this, idealism becomes unavoidable; for then we would be unable to reach objective reality by means of our ideas, as long as we have admitted that they do not enjoy essential disclosure of that reality.

In order for us to respond to this proof, we must know what is meant by the essential disclosure of knowledge. Essential disclosure means that knowledge shows us the object to which it is related as fixed in a reality external to the limits of our knowledge and consciousness. Our knowledge that the sun rises, and that the triangle is other than the square snakes us see the sunrise and the triangle's difference from the square as fixed in a reality independent of us. Hence,-this knowledge plays the role of a mirror, and its reflection of this independent reality to us is its essential disclosure. However, such a reflection does not mean that the sunrise truly exists outside, and that the triangle's difference from the square is fixed in reality. That is, the thing's fixedness in reality is other than its being also reflected. From this we know that the essential disclosure of knowledge is not detached from knowledge, even when there is error and ambiguity. The ancients' knowledge that the sun turns around the earth had the same degree of essential disclosure that our knowledge that the earth turns around the sun has. This means that they saw the sun's turning around the earth as something fixed in reality and independent of them. Thus, the objective existence of such turning was seen by them; that is, they believed it, even though it was not fixed in reality. [4]

Therefore, by knowledge of the assent type, human beings naturally move from conception to objectivity (p. 129) due to the essential disclosure of this knowledge. Whether knowledge is actually true or false, it is in either case knowledge and disclosure.

The fourth proof is that if knowledge of the assent type may be erroneous, and if its essential disclosure does not protect it from being so, then why is it not permissible that all our knowledge of the assent type is erroneous? Further, how can we rely on the essential disclosure of knowledge, as long as such disclosure is a necessary attribute of knowledge, both in its false and true matters alike?

This attempt differs in purpose from the previous attempt; for in the latter, idealism seeks to consider human knowledge as a subjective matter that does not pave the way to objective reality. But we have thwarted that attempt by showing the essential disclosure that distinguishes knowledge of the assent type from pure conception. The present attempt, on the other hand, seeks the total elimination of knowledge of the assent type from human thought. As long as such knowledge may be erroneous, or as long as its essential disclosure does not mean its constant truth, then why do we not doubt it and dispense with it altogether? If we do so, we will have nothing to secure the existence of the objective world.

Naturally, if human thought does not possess a number of pieces of knowledge whose truth is necessarily secure, such doubt will be unavoidable and inescapable. Further, it will be impossible for us to know any reality, regardless of its kind, as long as such knowledge does not rely on a necessary security [of truth], and as long as error is possible in every field. However, what overthrows this doubt is the rational doctrine which we had studied in the first chapter of the theory of knowledge, the primary source of knowledge. This doctrine asserts that there is necessary knowledge whose truth is secure, or completely free from error. Rather, error occurs sometimes in the method of making an inference from this knowledge. On the basis of this, human knowledge divides (as was pointed out (p. 130) in the above-mentioned discussion) into knowledge whose necessity is secure, of which the main principle of thought is formed, and secondary knowledge inferred from that principle. It is in this latter type of knowledge that error may occur. Thus, regardless of the degree of our doubt, we cannot doubt that principle, because its truth is necessarily secure.

We would now like to find out whether it is possible for the idealist philosopher, Berkeley, to deny that secure principle and reject the presence of primary necessary knowledge above error and ambiguity. There is no doubt that the answer is in the negative; for he is required to admit the presence of knowledge whose truth is secure, as long as he attempts to demonstrate his idealism by means of the previously mentioned proofs. A human being cannot demonstrate something, unless he based his demonstration on fundamentals and rules that are to him of secure truth. If we pay attention to Berkeley's proofs, we find him obliged to admit the following:

1. The principle of non-contradiction on which the first proof is based. If contradiction were possible, one could infer from the contradiction of sense perceptions that this principle is not objective.

2. The principle of causality and necessity. If Berkeley does not admit this principle, his proof will be useless. For a human being bases a proof on his opinion, only because he is convinced that a proof is a necessary cause of knowing the truth of that opinion. If he does not accept the principle of causality and necessity, the proof may be true, but still one cannot demonstrate by it the opinion under consideration.

If knowledge with secure truth is proved in human thought, then there is no (p. 131) doubt that our knowledge of the objective world which is independent of us is a part of this knowledge. The mind finds itself required to accept the existence of the external world as a whole, and to reject all doubt concerning it, regardless of the difference between the mind's awareness and actuality, or between the mind's thought and reality. Doubt concerning the existence of the independent world will be considered a kind of insanity. We conclude from our discussions of philosophical idealism that realism relies on two principles: the first is the acceptance of the essential disclosure of knowledge of the assent type, and the second is the acceptance of a basic principle of human knowledge whose truth is necessarily secure. We have already found that Berkeley is required to admit each of these two principles. Were it not for the essential disclosure of knowledge of the assent type, he would not have known other individuals, nor would he have fashioned his life on the basis of their existence. Also, were it not for knowledge whose truth is secure in the human thought, he would not have been able to demonstrate his idealistic claims.

Prior to the last century, physics used to explain nature in a materialistic, realistic fashion as governed by the general laws of mechanics. To the physicists, nature is real, in the sense that it exists independently of the mind and consciousness. It is also material because, according to their scientific analysis, nature is reduced to small, solid particles not receptive to change or division - such particles being the individual substances that were spoken of in Greek philosophy by Democritus. [40] These particles or primordial masses of nature are in constant motion. Matter is the sum of those particles, and the natural phenomena in it are the result of the spatial transposition and motion of those masses.

Since this motion requires scientific explanation, physics explained it mechanically, as it explained the motion of the pendulum of a clock or sound waves. (p. 132) It also assumed that those masses involved forces and specific relations among them in order to complete the mechanical explanation of the natural phenomena. These forces and relations must, in turn, also be subject to the mechanical explanation. Thus, the presumptive notion of air developed in physics, to which a number of functions were ascribed, such as the spreading of light that air was assumed to carry when moving from some masses to some others, as it carries heat, electricity and similar powers of nature. This discussion can be summed up in [the statement] that nature is a material, objective reality governed by a complete mechanical system.

But this physical notion was not able to remain steadfast in the face of modern discoveries that imposed on the scientists a total conversion of their theories about nature. Further, such discoveries proved to the scientists that the scientific mind is still at its beginning. The discovery of the electrons was one of the most important discoveries. It proved that the atom has a composite structure and that its radiation can be decomposed.

While the atom was the primary material unit of which nature is composed, it proved to be composite in turn. But this is not the whole story. It also became possible that the atom evaporates as electricity.

Moreover, while motion was restricted to the sphere of mechanical motion - this being consistent with the mechanical explanation of nature - other kinds of motion were discovered. Again, while the common view asserted that the material mass (this is the mathematical expression for the material substance) endures and cannot change, scientific evidence showed that it is not stable but relative, and that in the real sense, it does not express anything other than a latent power. That is why the bodily mass fluctuates in accordance with its motion.

Thus, it became dear to physicists that materialism had died out, and that the materialistic view of the world became inconsistent with science and the empirical evidence. (p. 183)

Due to this, the scientists were able to form a substantial notion of the world that is more profound than the materialistic notion. Materialism is just an aspect of this new notion. Indeed, some physicists went further than this to claim that the world can be attributed to pure motion. In this, they attempted to dispense with any substantial reality in addition to the world.

In the words of Ostwald: [41]

The stick that strikes Scaban? does not rise on the basis of the existence of the external world. This stick does not exist. The only thing that exists [of it] is its power of motion. [42]

Also, Karl Pearson [43] makes the following statement: 'Matter is the nonmaterial in motion.' [44]

In the midst of these new discoveries that shook the material edifice and showed that matter is a general human illusion about the world, and not a scientific notion that corresponds to the world, the idealistic tendency in physics arose and attracted many physicists. Thus, they said, because every day science offers a new evidence against the objective value of human knowledge and the material aspect of the world, atoms or the primary structures of matter become - after having disappeared in light of science nothing but convenient ways for expressing thought, and metaphors and signs that do not involve any objective reality. We are told by Eddington: [45]

There is nothing in the whole system of laws concerning natural science that cannot be inferred with clarity from the consideration of, and the reflection on the absolute comprehensive theory of knowledge. The mind, which does not know our existence, yet (p. 134) knows the order of thought by means of which it explains its empirical experience, is capable of attaining the whole knowledge of natural science which is acquired by way of sense experience. Finally, I say that what I know about the universe is truly and precisely the exact, the very thing which we add to the universe to make it intelligible. [46]

Later, Eddington expressed his hope that

What was concealed in the nucleus of the atom will become known in the very near future, in spite of the presumptions that our minds entertain, namely that this was concealed prior to our time. [47]

Actually, the idealistic tendency of these physicists was the result of an error in philosophical thinking, and not the result of a physical proof in the scientific field. The reason is that the primary issue in philosophy, the response to which divided philosophers into idealists and realists, appeared to them as fallacious. This primary issue is whether the world has an objective reality independent of our minds and consciousness. These physicists thought that this issue is subject to [one of the] following two responses only. Either the world is attributed to the mind and consciousness and, therefore, has no objective existence; or it is a material reality that exists outside the mind and consciousness.

If we discard the second response from the scientific proofs and experiments that showed that materialism is nothing but a veil covering the reality of the world, we are then required to adopt the first response and accept the pure idealistic notion of the world. However, the truth is that the two responses were not well stated above. The reason is (p. 135) that advancing opposition along idealistic lines does not require us to accept the necessity of the material aspect of objective reality. This is because realism, which is opposite idealism, does not mean more than the admission of an objective reality independent of the mind and consciousness. Whether this independent objective reality is matter, power, motion or electric waves is another question that realism, which accepts an objective world, must answer in light of science and the experimental discoveries. When we draw a complete distinction between the two issues, we can then attribute the abovementioned idealistic tendency to the error on which it rests.

We have already learned that the first question is this: 'Is the world a reality independent of the human mind?' The two responses to this question are given by idealism and realism. Idealism answers negatively, while realism answers affirmatively. Both answers must be based on purely philosophical grounds. Science and sense experience have no say in this matter.

The other question is the following: 'What is the independent objective reality; and are the qualities or properties of matter primary concomitants of it?'This question leans toward realism only, for there is no room for it on the basis of the idealistic notion.

Some realists answer it by offering a materialistic notion of the independent objective reality. Others offer different notions. The view of science determines some of these responses. Scientific experiments and discoveries form the realists' scientific notion of the objective world. Thus, if science discards the materialistic notion of the world, this will not mean that science rejects realism and has become idealistic. This is because scientific discoveries have not proved the non-existence of (p. 136) an independent objective reality. Rather, they have shown that the material aspect is not a necessary element of it. Whether the world is attributed to potency, motion or anything else other than matter is harmless to realism and cannot prove idealism, as long as the world has an objective reality that exists independently of the mind and consciousness. Thus, if in light of science, matter is transformed into electricity, mass into energy, energy into mass, and if nature expresses a motion free from matter - if all this comes true - it will not change our position at all concerning the first question. In any case, we believe that reality is not just a product of consciousness, but a product of the independent reality.

These scientific theories can make an impact if we have finished answering the first question and taken up the second question, in order to know the nature of the world. From this we learn that the discoveries of modern science do not refute realism at all. Instead, they refute materialism which claims to be the required description of that [objective] reality in general.

It is strange to find some materialists attempting to retain for materialism the same position that it had enjoyed, and to say that the scientific and empirical evidence does not demonstrate the non-existence of the material aspect of the world. Rather, it is a cause of strengthening our understanding of matter and its qualities.

Let us quote from Lenin:

The disappearance of matter determines that the degree of the knowledge of matter that we have reached also disappears, and that our awareness becomes more profound. Thus, some qualities of matter, such as its impenetrability, rest and mass, had appeared to us before as absolute, fixed and primary, but are now disappearing. They have become known as relative and necessary concomitants of some states of matter only. This is because the only property (p. 137) of matter, whose admission is determined by philosophical materialism, is the state of matter as an objective reality existing outside our awareness. [5]

The principles of the materialistic notion of the world cannot be shaken by any change in the scientific notion of the qualities of matter. This is not because what is philosophically known about matter has no relation to what is alleged to be scientifically known; but because it is impossible for matter to lose this quality of existing as an objective actual reality which is one of the basic qualities of matter.' [6]

By this, Lenin intended to falsify physical idealism and to strengthen his materialistic notion. However, it is clear from his words that he is ignoring every realistic philosophy, with the exception of the realistic philosophy that rests on material grounds. In order to resolve the contradiction between the materialistic notion and the truths of science and physics, he offered a strange explanation of the notion of matter. The explanation he gave was extensive and comprehensive enough to cover the objectivity and independence of the reality of matter. By means of this, he attempted to offer materialism instead of idealism as a unique philosophical solution for the issue of the existence of the world. It is clear that if matter is an exact expression of the independent objective reality, and if its only necessary quality is its existence and independence of our awareness, then theological metaphysics must be precisely a materialistic philosophy according to this new notion of matter. And thus, opposition between metaphysics and the materialistic philosophy and its notion of the world will be completely eliminated. (p. 138) The theological philosopher who accepts metaphysics says exactly the same thing about the world [as does the materialist]. The world, to him, is an objective reality independent of our awareness. The theological principle that is accepted by metaphysical philosophy is nothing but an objective reality independent of our awareness.

The truth is that it is useless to play with words. The expansion of the materialistic notion to the extent that would enable it to cover its opposite notion, and to be consistent with it does not mean anything other than its departure from its own philosophical reality, and its inability to respond to the notions that are its opposite.

Add to this that dialectical materialism does not permit Lenin to admit an absolute reality. For this would be contradictory to the dialectic which asserts the development of all realities in accordance with the contradictions that they involve. Is the basic quality of matter, in the new Leninian sense, an absolute quality that does not develop and does not submit to the law of dialectics and its contradictions? If the answer is in the affirmative, then the absolute reality that the dialectic rejects and that the Marxist dialectical principles do not accept must exist. If, on the other hand, this quality is a dialectical quality inclusive of the contradictions that cause it to develop and change, as do other realities in the world, this would mean that materialism also suffers from contradiction. Due to this, materialism had to change, to transform and to free itself from the basic quality of matter.

The conclusion that we can draw is that the idealistic tendency of the physicists was the result of failing to distinguish between the two philosophical issues discussed earlier, and not a direct product of scientific evidence.

In spite of this, we must point out another factor that played an important role in shaking the scientists' certitude about objective reality. This was the collapse of the scientific axioms in the modern scientific field. (p. 139) Thus, while such axioms had been considered absolute and indubitable truths, science succeeded in falsifying them and proving their erroneousness. With this, the atoms of John Dalton [48] quickly melted away, and the law of the imperishability of matter was shaken. Experiments showed that matter is an illusion that people held for thousands of years. As a reaction to this, doubt reappeared and took hold of the thoughts of a number of scientists. Thus, if the scientific axioms of yesterday are the errors of today, why should we not be doubtful about every reality, regardless of its clarity to us? Further, why should we assume the basic issue - that is, the issue of the existence of objective reality, to be above skepticism or doubt?

Hence, the idealistic tendency or agnosticism arose, not because science proved the correctness and soundness of this tendency, but because the scientists' conviction concerning science was shaken, and their faith in the absolute truth of its axioms collapsed.

However, this factor was only a psychological motive or a psychological crisis that inspired the inclination toward idealism. But this crisis is eliminated by little observation when the issue is studied philosophically. This is because the acceptance of the existence of the objective reality of the world is not the result of empirical and scientific proofs. We learned earlier that experiments cannot produce such an acceptance and move human beings from conception to objectivity. Rather, it is a natural and necessary acceptance in human nature. For this reason, it is general. Everyone shares in it, including the idealists who rebel against it verbally. They, too, have the very, same conviction, as their practical lives indicate.

All the axioms whose falsehood became evident centered on the structure of the objective world, and the determination of its primary reality and elements. It is clear that axioms of this sort are only confirmed by scientific experiments. Thus, their collapse and evident falsehood - whether due to the incompleteness or imprecision of the experiments on which these axioms rest, or to the unsoundness of the rational inference of the theory from the experiment - does not in any way mean that the necessary rational axioms may be false. (p. 140)

This is another sort of idealism adopted by some physiologists. According to their claims, it rests on the physiological truths that science discovers. This idealistic tendency proceeds from the following indisputable point.

The determination of the subjective form of the human sense perception depends on the composition of our senses and on the organic system in general. Thus, the nature of sense perception which comes to us from the external world does not by itself determine the form of the thing in our sense perception. Rather, this form is at the mercy of the nervous system more than anything else. On the basis of this, they claimed that the senses do not give us information about the external world. Rather, they inform us about our private organic system. This does not mean that the senses have no relation to external things. Rather, external things are the primary causes that produce the acts of sense perception. However, it is the nature of the private organic system that crystallizes the acts of sense perception in the manner in which sense perception expresses itself. Due to this, sense perception may be considered symbolic, and not an exact form. This is because a form is required to have some similarity to the thing that it represents. A symbol, on the other hand, need not have any similarity to the thing with which it is concerned.

This idealistic tendency is one of the unavoidable complications of the materialistic notion of knowledge which we completely reject. If knowledge were either nothing but a pure physiological act, or a specific material interaction between the nervous system and the external objective things, the quality of this physiological act must be linked either to the nature of the nervous system [alone], or to both the nature of this system and the nature of the objective things. Even if this leads to clear idealism and to the negation of the reality of the objective world, nevertheless, as long as we retain for external things the aspect of causing the processes of the nervous system, (p. 141) it is permissible to doubt the degree of correspondence between sense perception and objective reality, and to be skeptical as to whether knowledge is a mere specific reaction that indicates its cause symbolically, and without similarity [to it] in reality and content. We will soon return to this physiological idealistic notion.

The Defenders of Modern Skepticism

in fact, modern skepticism can be attributed to the old doctrine of skepticism that was upheld by the Greek school of skepticism headed by Pyrrho, who claimed that human beings are incapable of passing any judgement about things. Modern skepticism developed under circumstances similar to those that surrounded this old school and helped its growth. Greek skepticism arose as a compromise for the conflict that had reached its most intense moments between sophistry and philosophy. Sophistry was born a few centuries before philosophy. It rebelled against all truths and denied scientific and empirical propositions together. Philosophers confronted sophistry, pointing out its contradictions, and showing its collapse at the hands of criticism, until the wave of denial faded away. At that point, the notion of doubt asserting absolute agnosticism came about. It attempted to justify this agnosticism by showing the contradictions of the senses and the conflicting ideas that strip it of the quality of scientific confidence. Thus, it was a light form of sophistry. The same is true of modern skepticism. It attempted to advocate agnosticism as a solution for the contradiction between idealism and realism - if it is appropriate to consider surrendering to doubt as a solution for this contradiction. Due to this, it was a lighter form of idealism.

Modern skepticism did not rely on showing only the contradictions of sense perception and knowledge, but also on the analysis of knowledge which leads to doubt, according to the claims of its proponents. David Hume, who advocated the philosophy of skepticism as a result of Berkeley's philosophy, (p. 142) believed that certainty about the objective value of human knowledge is an inaccessible matter. The instrument of human knowledge is the mind or cogitation. It is impossible to have anything in the mind but knowledge. It is also impossible to conceive or to form the idea of a thing, if that idea is different from concepts and reactions. Let us direct our attention to the outside as much as we please, and let our imagination survey the skies or the furthest points of the universe, still we will never take one step beyond ourselves. Because of this, we cannot answer the basic issue in philosophy, concerning which the idealists and the realists fight. Idealism claims that reality is in consciousness and knowledge; while realism asserts that reality exists in an objective and independent manner. Skepticism, on the other hand, refuses to respond to this issue, because [according to it], it is impossible to give an answer to such an issue. Therefore, let this issue be suspended forever.

The fact is that David Hume did not add anything to Berkeley's proofs, even though he has strengthened doubt about realities and disregard for them. His skepticism was not limited to external matter. Rather, he struck down the two realities that Berkeley's philosophy retained - namely, the soul and God. This was in keeping with the extreme form of the empirical principle. For this purpose, he adopted the same Berkeleian style and method. As the material substance was not, in Berkeley's view, anything but an assembly of phenomena composed artificially in the mind, so also is the soul nothing but an assembly of internal phenomena and their relations. It is impossible to prove 'the I' (the self) by consciousness, because when I penetrate to the heart of what I call 'the 1', I come across a particular phenomenon. Thus, if all knowledge disappears, there will remain nothing that I can call 'the I'.

As for the idea of God, it rests on the principle of causality. However, it is not possible to admit the truth of this principle, according to Hume's claim. The reason is that the senses do not reveal to us a necessity between phenomena and events. Rather, the idea of causality is attributed to mere habit or to a form of association of ideas. (p. 143)

Thus, Hume reached the ultimate points of the empirical theory and the empirical doctrine to which this theory and this doctrine naturally lead. Instead of proving by this method [the necessity of] refuting the empirical or experimental principle in the mind, he was driven after this principle, until it led him to the unavoidable end.

We do not wish to discuss David Hume once again, inasmuch as his arguments are a repetition of Berkeley's proofs and views. Rather, we will take up one point only, namely habit, to which Hume attributed the principle of causality and many relations of things in the mind.

Let us therefore, ask: 'What is habit?' If it is nothing but a necessity existing between the idea of the cause and that of the effect, then it is another expression of the principle of causality. If, on the other hand, it is something else, then it is not different from causality in being an invisible idea to which we have no corresponding sense perception or reaction. But Hume must reject this [view], as he rejects all the truths that are inaccessible to the senses. In criticizing the empirical doctrine earlier, a response was given to this unsuccessful explanation of causality attempted by Hume. Therefore, let that [response] be attended to.

The Relativists

Relativism is considered one of the doctrines that assert the existence of reality and the possibility of human knowledge. However, this knowledge or reality, which the human mind may attain, is a relative knowledge and a relative reality, in the sense that it is not a reality free from subjective attachments, or an absolute reality. Rather, it is a mixture of the objective aspect of the thing and the subjective aspect of the knowing mind. Therefore, objective reality in thought is inseparable from the subjective aspect, and is not free from some foreign addition.

There are two main tendencies of relativism that differ in their idea about relativism and its limits in the human sciences. One of these is the tendency of relativism in the philosophy of Immanuel Kant. The other is the tendency of subjective relativism of a number of modern materialist philosophers. This latter tendency paved the way for developmental relativism, which was advocated by dialectical materialism. (p. 144)

To begin with, you must know that a rational judgement, according to Kant, is of two kinds. First, analytic judgement: this is the judgement that the mind uses for the purpose of clarification only, as in our statements: 'The body is extended', and 'The triangle is three-sided'. The source of the judgement here is the analysis of the notion of the subject, i.e. 'body', or 'triangle', the inference of the elements implied in this notion, such as'extension', which is implied in the notion of 'body' and 'three-sided', which is implied in the notion of 'triangle', and then the attribution of these elements to the subject. Analytic judgements do not give us new information about the subject. Their only role is to explain and clarify.

Second, synthetic judgement: this is the judgement whose predicate adds something new to the subject. Examples of this are: 'Bodies are heavy'. 'Heat expands corporeal particles.' 'Two plus two equals four.'

The quality that we impose on the subjects in these propositions is not inferred from them by analysis. Rather, it is additional. Because of this, a new knowledge that was not available before arises. Synthetic judgements are sometimes primary judgements, while at other times they are secondary judgements.

Primary judgements are those that are fixed in the mind prior to sense experience, such as mathematical judgements, as in our saying: 'A straight line is the shortest distance between two points.' The reason for their being so will be pointed out later. Secondary synthetic judgements, on the other hand, are those that are fixed in the mind after sense experience, such as the judgements: 'The sunlight warms the stone,' and 'Every body has a weight' (p. 145)

Kant's theory of knowledge may be summed up in the division of rational knowledge or judgements into three groups. [7]

1. Mathematics: all rational knowledge in this group is primary synthetic judgements prior to sense experience because it treats natural subjects in the human soul. Geometry specializes in space. The subject of arithmetic is number. Number is nothing but a repetition of the unit. Repetition means succession and following. And this is time, in the Kantian philosophical sense. Therefore, the two main poles around which the mathematical principles center are space and time. In Kant's view, space (p. 146) and time are two natural forms in people's formal sensibility. In other words, the form of space and that of time are present in the formal sensibility independently of sense experience. The consequence of this is that all the judgements related to time and space that we attribute to things are derived from our nature. In these judgements, we do not rely on what we acquire from the outside through the senses. That is why all mathematical propositions are derived from the nature of our minds. This means that we create them ourselves, and do not acquire them from the outside, since they focus on time and space that are natural. Thus, mathematics and the mathematical principles becomes knowable; and mathematical truths become absolutely certain. Therefore, there is no room in the mathematical field for error or contradiction, as long as this field is natural in the soul, and as long as its propositions are produced by us, and are not copied from an objective reality that is independent of us; so that we may doubt the extent of the possibility of knowing this reality and unraveling its innermost secret.
2. Natural science - that is, the human knowledge concerning the objective world that is subject to sense experience: here, Kant begins by dismissing matter from this field, because the mind does not know anything about nature other than its phenomena. He agrees with Berkeley that matter is not subject to knowledge and sense experience. However, he differs from Berkeley in another respect. He does not consider the above-mentioned point as a proof for the non-existence of matter and a philosophical justification for its denial, as Berkeley had claimed.