III The Empirical Theory
This theory states that only sense perception supplies the human mind with conceptions and ideas, and that mental power is that which reflects in the mind the various sense perceptions. Thus, when we perceive a thing, we can have a conception of it – that is, we can grasp its form mentally. But the ideas that lie outside the province of the senses cannot be created by the soul, nor constructed by it essentially and independently. According to this theory, the mind merely manages the conceptions of sensible ideas. It does this either (1) by combination and division, so that it combines those conceptions, or divides every one of them. Thus, it conceives ‘a mountain of gold’, or divides ‘the tree’, that is had known into pieces and parts. Or (2) the mind manages the conceptions of sensible ideas by abstraction and universalization, so that it separates the qualities of the form, and abstracts the form from its particular qualities; with the result that [the mind] can form from it a universal idea. This is exemplified in conceiving Zayd, and discounting all that which distinguishes him from ‘Umar. By means of this process of subtraction, the mind retains an abstract idea that applies to both Zayd and ‘Umar.
Perhaps the first one to advocate this empirical theory was John Locke, the eminent British philosopher who emerged in a philosophical period pervaded by the Cartesian notions of innate ideas. Thus, Locke began to refute these notions. For this purpose, he put forth in his book, Essay on Human Understanding, a detailed philosophy of human knowledge. In this book, he attempted to attribute all conceptions and ideas to the senses. Lacer, this theory became widely spread among European philosophers, and, to some extent, it destroyed the theory of innate ideas. A number of philosophers adopted its most extreme (p. 65) forms. This led to very dangerous philosophies, such as the philosophies of Berkeley and David Hume, as we will show later, God willing.
Marxism adopted this theory in its explanation of human knowledge. This was consistent with its view of human consciousness as a reflection of objective reality. Thus, all knowledge can be attributed to a reflection of a particular reality. Such a reflection occurs by means of the senses. It is not possible for knowledge and thought to be related to anything that falls outside the limits of sensible reflections. Hence, we do not conceive anything other than our sense perceptions which indicate objective realities that exist in the external world.
Georges Politzer  said the following:
The Marxist view, therefore, can be interpreted to mean that there is no source for the content of our consciousness other than the objective particulars which are given to us by the external circumstances that we live. These particulars are given to us through sense perceptions. That is all there is to this matter. 
Such experiments – if sound- prove scientifically only that the senses are the primary source of conception. Were it not for the senses, no conceptions would have existed in the human mind. However, such experiments do not strip the mind of the ability to produce from the sensible ideas new ideas not known by the senses. Therefore, it is not necessary that all our simple conceptions be preceded by the sense perception of their ideas, as the empirical theory claims. In light of the above-mentioned experiments, the senses are the primary structure on the basis of which the human conception is established. But this idea does not mean that the mind is void of agency and innovation of new conceptions in light of the conceptions that are derived from the senses.
It is possible for us to show the failure of the empirical theory in its attempt to attribute all the human conceptual notions to the senses by investigating a number of the notions of the human mind, such as the following: ’cause’ and ‘effect’, ‘substance’ and ‘accident’, ‘possibility’ and ‘necessity’, ‘unity’ and ‘multiplicity’, ‘existence’ and ‘non-existence’, as well as other similar notions and conceptions.
We all know that the senses grasp the cause and effect themselves. (p. 67) Thus, by means of our sight, we know that a pencil falls to the ground if the table on which it was placed is pulled from underneath it. Also, by means of touch, we know that water becomes hot when it is placed on fire. Similarly, we know chat bodily particles expand in hot weather. In these examples, we perceive two successive phenomena, but we do not perceive a specific relation between the two. This relation is what we call ‘causality’. By ‘causality’ we mean the influence of one of these phenomena on the other and the need of the other for it, in order that the other exists.
The attempts that seek to extend the province of the senses to cover causality itself and to consider it as an empirical principle are based on avoiding the depth and precision in the knowledge of the realm of the senses and the ideas and limits it includes. Regardless of the proclamations made by the empiricists – namely, chat human experiences and the experimental sciences, which are based on the senses, are what clarify the principle of causality, and make us realize how specific material phenomena arise from other similar phenomena – I say that regardless of such proclamations, the empiricists will not be successful, as long as we know that scientific experiments cannot reveal by means of the senses anything except the succession of phenomena. Thus, we can know that by placing water on the fire, the water gets hot. Then we multiply its temperature. At last, we perceive the boiling of the water. The empirical side of the experiment does not disclose that boiling is produced because the temperature reaches a specific degree. But if our empirical experiments fall short of disclosing the notion of causality, then how did this nation develop in the human mind, so that we began to conceive it and think about it?
David Hume, one of the advocates of the empirical principle, was more precise than others in applying the empirical theory. He knew that causality, in the real sense of the term, cannot be known by the senses. Because of this, he rejected the principle of causality and attributed it to the habit of the association of ideas, saying that I see the billiard ball move, and then encounter another ball that, in turn, moves. But in the movement of the former ball, there is nothing that reveals to me the necessity of the movement of the latter. The internal senses also tell me that the movement of the organs follows upon an order from the will. However, they do not give me a direct knowledge of a necessary relation between the movement and the order.  (p. 68)
But the rejection of the principle of causality does not at all minimize the difficulty that faces the empirical theory. The rejection of this principle as an objective reality means that we do not believe that causality is a law of objective reality, and that we are unable to know whether the phenomena are linked by necessary relations that make some of them effects of some others. However, the principle of causality as an idea assented to is one thing, while the principle of causality as a conceptual idea is another. Suppose, for example, that we do not assent to the fact that some sensible things cause some other sensible things, and chat we do not form an assent concerning the principle of causality, would this mean that we do not have a conception of the principle of causality either? If we do not have such a conception, then what is it chat was rejected by David Hume? Can a human being reject something of which he has no conception?
The undeniable truth is chat we conceive the principle of causality, whether or not we assent to it. Further, the conception of causality is not composed of the conceptions of the two successive things. When we conceive the causation of a specific degree of temperature for boiling, we do not intend by this causation an artificial composition of the idea of temperature and that of boiling. Rather, we intend a third idea that exists between the two. From where, then, does this third idea that is not known by the senses come, if the mind does not have the ability to create non-sensible ideas? We face the same difficulty with regard to the other notions mentioned earlier;  since all of them are non-sensible. Thus, it is necessary to cast aside the purely empirical explanation of human conceptions and to adopt the dispossession theory (nazariyyat al-intiza).