Theory of Vision in Mulla Sadra’s Philosophy

Husein Masumi Hamedani

 

What Mulla Sadra suggests in his theory of vision does not add anything new to the content of his general theory of perception, thus one can safely conclude that the former theory is secondary to the latter. Accordingly, the writer has decided not to discuss the details of the theory of vision here and only suffice to explaining the nature and epistemological aspects of Mulla Sadra’s theory in this regard. To accomplish this task, he has used two terms which have also been used in discussing the theory of perception. It should be noted, however, that the writer has not coined these terms himself, and that he has only transferred them from one theory to another. Therefore, in what follows, the theory of vision will be studied and propounded from both transcendental and scientific perspectives. Here, the writer intends to prove that Mulla Sadra’s theory of vision is the most sublime of all transcendental theories concerning vision and show its relation to scientific theories.

The author’s approach to this problem is a historical one, since he works in the field of the history of science. Thus he must initiate his discussion from the related views in the past, beginning with Aristotle, continuing with the ideas of some Islamic philosophers, and finally coming to Mulla Sadra, to be able to explain the above two perspectives.

The sense of vision has always had a specific place among human senses since long ago. This place has been celebrated not only in literature but also in art. We can see an object, but we can only smell its odor or hear its sound. It seems as if the sense of vision deals with the object itself, while the subjects of other senses are some of the accidents of the object, including its odor or sound. This superior position of vision has been both confirmed and rejected in Aristotelian philosophy. On the one hand, in one place Aristotle says that vision is higher than all other senses; on the other hand, in some other place he maintains that the subject of vision is not the object itself; rather, like all other senses, its subject (or its main subject) is one of the accidents of the object such as its color. The subject of vision should not be mistaken for its conditions. What we see is color; however, color is not visible by itself. For objects to be seen, some conditions should be met:

1. Presence of light

 A colored object which is the subject of vision should either be luminous (reflect light by itself) or to be lit up by another luminous object. Aristotle’s view as to whether luminous objects are seen by themselves or should be colored to be seen is not quite clear.

2. Presence of a transparent medium between the eye and the object

The transparent medium is not visible by itself. Thus one of the conditions for the object’s being visible is to be opaque. Nevertheless, other objects are visible only when there is a transparent medium like water, air, glass, or some other mineral substance between them and the eye.

In Aristotle’s view, the important point is that although these mediums are transparent, their transparency is not due to their specific physical structure or the existence of a common material part in all of them; these mediums are transparent because they possess a source of transparency. Aristotle calls this source of transparency diaphane. From now on, when speaking of Aristotle, instead of transparent or transparency, we will use the term diaphane, which he used for both terms. Diaphane is neither an object nor a part of the object. 

When we say light, we mean the highest level of transparency, since it is transparent. Likewise, when we speak of one’s walking alongside a road, we are in fact referring to the very property of a road which is being used for walking. Of course, assimilating diaphane or the transparent medium to a road might mislead us to think that as the road is the passageway for a passenger, there is a space in which the passenger moves from one place to another to reach a destination from a source. And therefore, diaphane, too, should be the passageway for light or a space in which the light moves to reach from the view to the viewer. However, this is by no means what Aristotle and Ibn Sina have in mind. Concepts such as light transfer, in the sense of the transference of a physical object, are not at all compatible with Aristotle and Ibn Sina’s way of thinking. An important part of Ibn Sina’s writings about vision in al-Shifa’ is devoted to the rejection of such ideas. Nevertheless, before dealing with Ibn Sina’s views in this regard, we will ponder a little more over Aristotle’s theory of vision and its epistemological aspect, as well as over another epistemological theory of vision.

In the above, the author tried to explain the concept of diaphane by resorting to the simile of the road, which might lead to some kind of misunderstanding. He has also used a denomination to propound the epistemological place of Aristotle’s theory. The term used here is useful for orienting the mind; however, since it belongs to the history of modern philosophy, its application to Aristotelian theory, while illuminating some of its aspects, might create some misunderstandings in certain respects.

After this introduction and after giving this warning, the author explicitly maintains that Aristotle’s theory of vision is mainly a transcendental one. Here, the term transcendental is used in Kantian sense. In his philosophy, or at least in his Critique of Pure Reason, Kant does not intend to devise a philosophical physics versus Newtonian physics. Contrarily, by acknowledging its correctness, he intends to describe the kind of world or existents that Newtonian physics applies to. In other words, he aims to recount the prerequisites necessary for this kind of physics, which is absolutely correct, to be applicable, and also to explain the existents’ behavior after these prerequisites are materialized. This is a question which was of great interest to Kant, the writer of Critique of Pure Reason; nevertheless, he excludes it from the domain of his works and studies.

Aristotle’s theory of vision can be considered a transcendental one in the light of the fact that, like Kant, he does not deal with how visual perception occurs; rather, he intends to clarify the nature of the conditions which are necessary for us to see the objects.

Nevertheless, this is the only similarity between the theories of Kant and that of Aristotle, since, unlike Kant’s theory, in which these conditions belong to the subject, in Aristotle’s theory, the conditions for vision, including being colored, possessing light, being in front of something, the existence of a transparent medium or diaphane, all belong to the object, or at least to the outside world. On the other hand, employing the term transcendental for referring to Aristotle’s theory in comparison to Kant’s theory raises another question.

As mentioned before, after enumerating the aproiri conditions for having the experience of vision, Kant refers us to Newtonian physics to explain the scientific mechanism resulting from this experience. Now the question is to which theory Aristotle refers us when speaking of the mechanism of vision. A tentative answer here is that a part of this mechanism is explained by Aristotle himself. In other words, his theory of vision is not a perfectly transcendental one, that is, Aristotle does not suffice to explaining the conditions for vision; rather, he details its mechanism to some extent. However, his explanation in this regard is quite short and ambiguous. He maintains that when the necessary conditions are materialized, the forms of objects or their phantoms are reached to the eye. The first place where these phantoms are formed or perceived is the external surface of the eye or the crystalline lens. Accordingly, visual perception begins from the most external surface of the eye.

From one aspect, the above explanation of objects is satisfactory, since any theory about visual perception is supposed to explain why what we see is similar to objects. Apparently, Aristotle, through maintaining that the forms of objects come to the eye after the conditions referred to previously are provided, intends to explain the very similarity between the object and what the eye perceives. Yet, the problematic point is what he means by these forms, and in what sense he is using the words ‘form’ and ‘phantom’.

According to the comparison made above, to explain some physical and mechanical phenomena, Kant could refer to certain established facts in mechanics. And as mentioned before, when speaking of the science of mechanics, Kant refers to Newtonian mechanics. Therefore, one might ask: “What does Aristotle mean by the science of optics?” The optics or the science of perspectives Aristotle refers to addresses one of the sciences branching from mathematics at his time. This field of study explained the mechanism of vision as a physical phenomenon rather than a physiological or psychological one. This science, some of whose early written texts have remained a little after Aristotle’s death, i.e., 300 B.C., like Euclidian optics, was quite common in the world of Islam, or, at least, in many places, on the basis of some subjects or postulates and by means of geometrical reasoning, it was capable of explaining why we see farther objects smaller than their real size or the nearer objects bigger, why we see something above something else while it is not there, or why we see something which is on the left of something else on its right side, and vise versa.

The science of optics discussed above was based on the assumption that vision is caused by discrete rays which emanate from the eye in the form of a cone whose apex is in the eye. Such rays were called visual or radial rays and the cone was called the visual cone. Vision was believed to be completed through the mediation of this cone or these rays in the different versions of this theory. There were different views as to the discreteness of these rays and their genus. However, all thinkers unanimously maintained that, firstly, visual perception is the result of the emanation of something from the eye towards the object rather than vice versa; secondly, visual perception begins exactly from the moment the thing emanating from the eye reaches the surface of the object. Therefore, according to this theory, to see something, it is not necessary to wait for these rays or fluid things that emanate from the eye to return to the eye and touch its surface. These rays function like the rays of modern radars, which immediately after confronting an obstacle sense it. In other words, these rays or fluid things were considered to be sensitive, function like sensors, and be the continuity or extension of the eye, like man’s arm, which is the extension of his body, or like a stick which functions as the extension of man’s arm and, in a sense, could be said to feel the obstacles.

The author calls this theory of vision the scientific theory, since it aims at explaining the mechanism of vision rather than the required conditions for vision to be realized. However, using this attribute to refer to this theory is not intended either to confirm or reject it. The author only intends to have given a name to this theory versus transcendental theories. Of course, such a denomination is not much unjustified, since like many other new scientific theories, this theory explains the mechanism of vision and possesses a mathematical structure.

When we call this theory scientific, we mean that it is predominantly scientific (as we consider Aristotle’s theory as being predominantly transcendental); however, it is not void of the elements and features of a transcendental theory. For example, we can read about the conditions of the realization of vision in Ptolemy’s book of optics, in which he almost refers to the same things that were previously quoted from Aristotle.

In the world of Islam, such theories are called the theory of the people of ray, and, in contrast, they refer to those of the type of Aristotle’s theory as the theory of the people of impression. Obviously, these two theories are exclusive and one cannot believe in both of them at the same time. In his book, On the Soul, Aristotle explains vision on the basis of the theory of impression and refers to it in several places to prove his points. Whatever the truth, when we come from Aristotle to Ibn Sina, the situation changes.

The third article of the sixth art of Tabi‘iyyat (Physics) of al-Shifa is devoted to the discussion of vision, and is considered one of the most important texts in Islamic philosophy in this regard. Unfortunately, this text has been examined very little, if at all. In this article, apart from explaining the general views of the people of impression, Ibn Sina rejects the theory of the people of ray; however, the interesting point is that he refutes not only the view of those believing that a ray emanates from the eye and reaches the object, i.e., the theory of the people of ray in its common and general sense, but also the view of those believing that a ray emanates from the object and reaches the eye. According to the second view, a material thing, for example, a bodily substance or a collection of atoms, emanates from the object in the form of a flood and reaches the eye through the air. Such particles impress the eye and we see the object. Ibn Sina, in fact, tries to prove that the impression he talks about is other than impression in the sense of the formation of a material picture in the eye through being hit by some atoms or the transference of a material object.

Taking the above explanations into account, although Ibn Sina’s theory could be considered even more transcendental in nature than that of Aristotle in the sense discussed previously, it is to some extent a scientific one. This is because Ibn Sina still conceives of vision as the impression of the form of the object on the crystalline lens, and, particularly, even believes that some of the extrinsic senses of visible objects could only be explained by the people of ray. In his Danishnama-i  ‘al’ai and ‘Ayen al-hikma, Ibn Sina, on the basis of an unfortunately incorrect geometrical reasoning proves that it is only through the theory of the impression of the form of objects on the eye that one can explain why farther objects are seen smaller, while in his view, which is also incorrect, the theory of the people of ray is incapable of explaining such concepts. The theories posed so far concerning vision have all been more or less mixed ones. The theories of Aristotle and Ibn Sina are primarily transcendental with a little scientific flavor in some places, and the theories of Ptolemy and the people of ray are generally scientific ones with a little transcendental flavor in parts. In contrast to these theories, Mulla Sadra and Suhrawardi’s theory of vision can be considered a purely transcendental one. In the sixth part of the fourth chapter of the fourth journey in al-Asfar, after stating the theories of the people of ray and the people of impression and rejecting them, Mulla Sadra writes:

The view attributed to illuminationists and adopted by Shaykh Ishraq is that there is neither a ray nor an impression at work in vision. Rather, vision is completed only when the enlightened object (the object upon which light has been reflected) is located in front of the vision organ. When these conditions are realized, and when there is no obstacle, the soul develops an illuminative knowledge by presence of the enlightener and observes it clearly. This theory talks about the external and material conditions for vision, including the existence of the enlightened object, the object’s being in front of the eye, the smooth and slippery nature of the object’s surface, and the absence of an obstacle, rather than the formation of an image of the object in the eye or the visual rays’ giving information of the object to the eye. In other words, in this theory, although the subject of perception is the same external object or its form, the cause of perception is not the external object anymore.

In Mulla Sadra’s view, the flaw of this theory is that there the object is in the outside, while it is the cause of the soul, and, according to Mulla Sadra’s general theory of perception, this is not possible. Therefore, he believes that if the cause of perception is the soul, its effect, which is the perceived, should be in the soul as well (It is emphasized that the author is mainly reporting Mulla Sadra’s views, without taking any side).

Mulla Sadra’s specific view is that when the conditions for vision are provided, a form is constructed in the soul which is separate, not in the sense that this soul has abstracted the form from the external object, or that it accepts this abstract form from the external world, rather it constructs this form by itself, and it is the form which is both the actual sensor and the actual sensible. As Mulla Sadra stipulates, his view of the soul has been derived from his general view of perception. This point is known to everyone, and its philosophical consequences have been discussed in several places. The question which is raised here is whether this transcendental theory necessitates the formulation of the scientific theory of vision or not.

In chapter seven of the fourth journey in al-Asfar, Mulla Sadra quotes all the arguments for and against the theories of impression and ray, and, almost on behalf of either side, tries to answer the questions of the other side; however, he tries to remove some ambiguities and problems on the basis of his own theory. For example, when rejecting the view of the people of ray or that of the people of impression, it seems as if he considers his theory as a rival to their theories, comparable to them, and of the same kind. Later in the eighth chapter of the same discussion, under what the people of ray maintain, he asserts that he adopts the science of optics as the science of perspectives. However, he tries to provide some justifications for the soundness of this science. He argues that when an object is placed in front of the eye, the eye naturally functions like a point. When a point is in front of an object, the relation can be shown in the form of a cone. Thus the cone they believe in is not much far from reality. On the other hand, he denies saying that a ray does not emanate from the eye, or that it does not reach the eye; he only states that the real perceiver is the soul, and that the real perceived is in fact in the soul.

Nevertheless, in spite of the justification he presents for the visual cone, and the agreement he talks about between his chosen doctrine and that of the people of ray, he asserts that these two theories might be similar in many of their consequences and concomitants without being the same. Although he refers to the visual cone, and although he talks about the commonalities between his own theory and that of the people of ray with respect to several concomitants, the truth is that his theory of vision is as much in agreement with the theory of the people of ray as it is with the theory of the people of impression. ‘Allamah Tabataba’i has implicitly referred to this point in some of his glosses on the related parts of al-Asfar.

Therefore, we cannot call Mulla Sadra’s theory a wrong one simply because he personally believes in the theory of the people of ray in science of perspectives and optics. The problem (in the positive sense of the word) with his theory of perception and vision and theory of perception in general is not their agreement or disagreement with this or that scientific theory. The problem, advantage, or salient feature of his theories is their suggesting that even if we try to open more of the links of the chains of material causes and effects, not even the last link will be connected to the sublime threshold of the soul.