A History of Mediaeval Jewish Philosophy

by Isaac Husik

power. Divide into the several parts ab, be, cd, de, etc. If every one of the parts has an infinite power, ab has an infinite power, ac a greater infinite power, ad a still greater, ae a still greater, and so on. But this is absurd, for there cannot be anything greater than the infinite. It follows then that each of the parts has a finite power; and as the sum of finites is finite, the line ae also has a finite power. All these principles we must keep in mind, for we shall by means of them prove later the existence and incorporeality of God.[235]

As the concepts of physics are essential for proving the existence of God, so are the principles of psychology of importance in showing that there are intermediate beings between God and the corporeal substances of the world. These are called in the Bible angels. The philosophers call them secondary causes.

Accordingly Ibn Daud follows his physical doctrines with a discussion of the soul. There is nothing new in his proof that such a thing as soul exists. It is identical with the deduction of Joseph Ibn Zaddik (supra, p. [134]). Stone and tree and horse and man are all bodies and yet the last three have powers and functions which the stone has not, viz., nutrition, growth and reproduction. Horse and man have in addition to the three powers above mentioned, which they have in common with tree, the powers of sensation and motion and imagination, which plants have not. Finally man is distinguished above all the rest of animal creation in possessing the faculty of intelligence, and the knowledge of art and of ethical discrimination. All these functions cannot be body or the result of body, for in that case all corporeal objects should have all of them, as they are all bodies. We must therefore attribute them to an extra-corporeal principle; and this we call soul. As an incorporeal thing the soul cannot be strictly defined, not being composed of genus and species; but we can describe it in a roundabout way in its relation to the body. He then gives the Aristotelian definition of the soul as "the [first] entelechy of a natural body having life potentially" (cf. above, p. [xxxv]).

Like many of his predecessors who treated of the soul, Ibn Daud also finds it necessary to guard against the materialistic theory of the soul which would make it the product of the elemental mixture in the body, if not itself body. This would reduce the soul to a phenomenon of the body, or in Aristotelian terminology, an accident of the body, and would deprive it of all substantiality and independence, not to speak of immortality. How can that which is purely a resultant of a combination of elements remain when its basis is gone? Accordingly Ibn Daud takes pains to refute the most important of these phenomenalistic theories, that of Hippocrates and Galen. Their theory in brief is that the functions which we attribute to the soul are in reality the results of the various combinations of the four elementary qualities, hot, cold, moist, dry. The more harmonious and equable the proportion of their union, the higher is the function resulting therefrom. The difference between man and beast, and between animal and plant is then the difference in the proportionality of the elemental mixture. They prove this theory of theirs by the observation that as long as the mixture is perfect the activities above mentioned proceed properly; whereas as soon as there is a disturbance in the mixture, the animal becomes sick and cannot perform his activities, or dies altogether if the disturbance is very great. The idea is very plausible and a great many believe it, but it is mistaken as we shall prove.

His refutation of the "accident" or "mixture" theory of the soul, as well as the subsequent discussion of the various functions, sensuous and rational, of the tripartite soul, are based upon Ibn Sina's treatment of the same topic, and we have already reproduced some of it in our exposition of Judah Halevi. We shall therefore be brief here and refer only to such aspects as are new in Ibn Daud, or such as we found it advisable to omit in our previous expositions.

His main argument against the materialistic or mechanistic theory of the soul is that while a number of phenomena of the growing animal body can be explained by reference to the form of the mixture in the elementary qualities, not all aspects can be thus explained. Its growth and general formation may be the result of material and mechanical causes, but not so the design and purpose evident in the similarity, to the smallest detail, of the individuals of a species, even when the mixture is not identical. There is no doubt that there is wisdom here working with a purpose. This is soul. There is another argument based upon the visible results of other mixtures which exhibit properties that cannot be remotely compared with the functions we attribute to the soul. The animal and the plant exhibit activities far beyond anything present in the simple elements of the mixture. There must therefore be in animals and plants something additional to the elements of the mixture. This extra thing resides in the composite of which it forms a part, for without it the animal or plant is no longer what it is. Hence as the latter is substance, that which forms a part of it is also substance; for accident, as Aristotle says, is that which resides in a thing but not as forming a part of it.

We have now shown that the soul is substance and not accident. We must still make clear in which of the four senses of the Aristotelian substance the soul is to be regarded. By the theory of exclusion Ibn Daud decides that the soul is substance in the sense in which we apply that term to "form." The form appears upon the common matter and "specifies" it, and makes it what it is, bringing it from potentiality to actuality. It is also the efficient and final cause of the body. The body exists for the sake of the soul, in order that the soul may attain its perfection through the body. As the most perfect body in the lower world is the human body, and it is for the sake of the soul, it follows that the existence of the sublunar world is for the sake of the human soul, that it may be purified and made perfect by science and moral conduct.

While we have proved that soul is not mixture nor anything like it, it is nevertheless true that the kind of soul bestowed upon a given body depends upon the state of the mixture in the elementary qualities of that body. Thus we have the three kinds of soul, vegetative, animal and human or rational. We need not follow Ibn Daud in his detailed descriptions of the functions of the several kinds of soul, as there is little that is new and that we have not already met in Joseph Ibn Zaddik and Judah Halevi. Avicenna (Ibn Sina) is the common source for Halevi and Ibn Daud, and the description of the inner senses is practically identical in the two, with the slight difference that Halevi attributes to the "common sense" the two functions which are divided in Ibn Daud between the common sense and the power of representation.

The soul is not eternal. It was created and bestowed upon body. When a body comes into being, the character of its mixture determines that a soul of a certain kind shall be connected with it. The other alternatives are (1) that the soul existed independently before the body, is then connected with the body and dies with the death of the latter; or (2) it remains after the death of the body. The first alternative is impossible; because if the soul is connected with the body in order to die with it, its union is an injury to the soul, for in its separate existence it was free from the defects of matter. The second alternative is equally impossible; for if the soul was able to exist without the body before the appearance of the latter and after its extinction, of what use is its connection with the body? Far from being of any benefit, its union with the body is harmful to the soul, for it is obliged to share in the corporeal accidents. Divine wisdom never does anything without a purpose.