A History of Mediaeval Jewish Philosophy

by Isaac Husik

Finally Ibn Daud finds it necessary to defend the Bible against those who criticize the Jews on the ground that there is no mention of the future world and the existence of the soul after death in the Biblical writings. All the rewards and punishments spoken of in the Bible, they say, refer to this world. His answer offers nothing new. Judah Halevi had already tried to account for this phenomenon, besides insisting that altogether devoid of allusion to the future world the Bible is not. Ibn Daud follows in Halevi's footsteps (cf. above, p. [170]).[236]

Abraham Ibn Daud closes the first, the purely scientific part of his treatise, by a discussion of the heavenly spheres and their motions. In accordance with the view of Aristotle, which was shared by the majority of writers throughout the middle ages, he regards the spheres with their stars as living beings, and their motions as voluntary, the result of will and purpose, and not simply "natural," i. e., due to an unconscious force within them called nature. One of his arguments to prove this is derived from the superiority of the heavenly bodies to our own. Their size, their brightness and their continued duration are all evidence of corporeal superiority. And it stands to reason that as the human body, which is the highest in the sublunar world, has a soul that is nobler than that of plant or animal, so the heavenly bodies must be endowed with souls as much superior to the human intellect as their bodies are to the human body. The Bible alludes to this truth in the nineteenth Psalm, "The heavens declare the glory of God.... There is no speech nor language...." The last expression signifies that they praise God with the intellect. There are other passages in the Bible besides, and particularly the first chapter of Ezekiel, which make it clear that the heavenly bodies are living and intelligent beings; not, to be sure, in the sense of taking nourishment and growing and reproducing their kind and making use of five senses, but in the sense of performing voluntary motions and being endowed with intellect.[237]

We have now concluded our preliminary discussion of the scientific principles lying at the basis of Judaism. And our next task is to study the fundamental doctrines of Jewish theology which form the highest object of knowledge, dealing as they do with God and his attributes and his revelation. The first thing to prove then is the existence of God, since we cannot define him. For definition means the designation of the genus or class to which the thing defined belongs, whereas God cannot be put in a class. As the essence of a thing is revealed by its definition, we cannot know God's essence and are limited to a knowledge of his existence.

The principles for this proof we have already given. They are that a thing cannot move itself, and that an actual infinite series is impossible. The argument then proceeds as follows: Nothing can move itself, hence everything that moves is moved by something other than itself. If this is also moving, it must be moved by a third, and so on ad infinitum. But an actual infinite series of things moving and being moved is impossible, and unless we ultimately arrive at a first link in this chain, all motion is impossible. Hence there must be a first to account for the motion we observe in the world. This first must not itself be subject to motion, for it would then have to have another before it to make it move, and it would not be the first we supposed it to be. We have thus proved, therefore, the existence of a primum movens immobile, a first unmoved mover.

We must now show that this unmoved mover is incorporeal. This we can prove by means of another principle of physics, made clear in the first part. We showed there that a finite body cannot have an infinite power. But God is infinite. For, being immovable, his power is not affected by time. Hence God cannot be body.

This proof, as we said before, is new in Jewish philosophy. In Bahya we found a proof which bears a close resemblance to this one (cf. above, p. [87]); but the difference is that Bahya argues from being, Ibn Daud from motion. Bahya says if a thing is, some cause must have made it to be, for a thing cannot make itself. As we cannot proceed ad infinitum, there must be a first which is the cause of the existence of everything else. The objection here, of course, is that if a thing cannot make itself, how did the first come to be.

The Aristotelian proof of Ibn Daud knows nothing about the origin of being. As far as Aristotle's own view is concerned there is no temporal beginning either of being or of motion. Both are eternal, and so is matter, the basis of all genesis and change. God is the eternal cause of the eternal motion of the world, and hence of the eternal genesis and dissolution, which constitutes the life of the sublunar world. How to reconcile the idea of eternal time and eternal motion with the doctrine that an actual infinite is impossible we shall see when we treat Maimondes (p. [251]). Ibn Daud does not adopt eternity of motion even hypothetically, as Maimonides does. But this merely removes the difficulty one step. For the infinity which is regarded impossible in phenomena is placed in God. But another more serious objection is the adoption of an Aristotelian argument where it does not suit. For the argument from motion does not give us a creator but a first mover. For Aristotle there is no creator, and his proof is adequate. But for Ibn Daud it is decidedly inadequate. We are so far minus a proof that God is a creator ex nihilo. Ibn Daud simply asserts that God created matter, but this argument does not prove it. As to the incorporeality of God Aristotle can prove it adequately from the eternity of motion. If a finite body (and there is no such thing as an infinite body) cannot have an infinite power, God, whose causing eternal motion argues infinite power, is not a body. Ibn Daud's attempt to prove God's infinity without the theory of infinite motion on the ground that time cannot affect what is immovable, is decidedly less satisfactory. On the whole then this adoption of Aristotle's argument from motion is not helpful, as it leads to eternity of matter, and God as the mover rather than the Creator. Gersonides was frank enough and bold enough to recognize this consequence and to adopt it. We shall see Maimonides's attitude when we come to treat of his philosophy.

Ibn Daud may have been aware of the inadequacy of his argument from motion, and therefore he adds another, based upon the distinction between the "possible existent" and the "necessary existent"—a distinction and an argument due to Alfarabi and Avicenna. A possible existent is a thing whose existence depends upon another, and was preceded by non-existence. It may exist or not, depending upon its cause; hence the name possible existent. A necessary existent is one whose existence is in itself and not derived from elsewhere. It is a necessary existent because its own essence cannot be thought without involving existence. Now the question is, Is there such a thing as a necessary existent, or are all existents merely possible? If all existents are possible, we have an infinite series, every link of which is dependent for its existence upon the link preceding it; and so long as there is no first there is nothing to explain the existence of any link in the chain. We must therefore assume a first, which is itself not again dependent upon a cause prior to it. This is by definition a necessary existent, which is the cause of the existence of everything else. This proof is compatible with God as a Creator.

Having shown the existence and incorporeality of God we must now prove his unity. We shall base this proof upon the idea of the necessary existent. Such an existent cannot have in it any multiplicity; for if it has, its own essence would not be able to keep the elements together, and there would be need of an external agent to do this. But in this case the object would be dependent upon something else, which is incompatible with the idea of a necessary existent.

Nor is it possible there should be two necessary existents; for the necessary existent, we have just shown, must be of the utmost simplicity, and hence cannot have any attribute added to its essence. Now if there is a second, there must be something by which the first differs from the second, or they are identical. Either the first or the second therefore would not be completely simple, and hence not a necessary existent.