Some think that because the soul is the form of the body it is dependent upon it and cannot survive it, as no other form survives its substance. But this inference is not valid. For if the human soul is included in the statement that no form survives its matter, we assume what we want to prove, and there is no need of the argument. If it is not as a matter of fact included, because it is the question at issue, its comparison with the other observed cases is simply a matter of opinion and not decisive.
The reader will see that the problem of the rational soul gave Ibn Daud much concern and trouble. The pre-existence of the soul as Plato teaches it did not appeal to him for many reasons, not the least among them being the statement in Genesis (2, 7), "And God breathed into his nostrils the breath of life," which seems to favor the idea of the soul originating with the body; though, to be sure, a harmless verse of this kind would not have stood in his way, had he had reason to favor the doctrine of pre-existence. Immortality was also a dogma which he dared not deny. The arguments against it seemed rather strong. From the doctrine of the soul's origin with the body and its being fitted to the material composition of the latter, would seem to follow the soul's extinction with the death of the body. The same result was apparently demanded by the observation that the intellect develops as the body matures, and that without the senses and their data there would be no intellect at all. The fluctuation of intellectual strength with the state of bodily health would seem to tend to the same end, against the doctrine of immortality. Moreover, the Aristotelian definition of the soul as the entelechy or form of the body, if it applies to the rational faculty as well as to the lower powers, implies necessarily that it is a form like other forms and disappears with the dissolution of its substance. To avoid all these pitfalls Ibn Daud insists upon the incorporeal character of the reason's activity, _i. e._, its independence of any corporeal organ, and its increasing power in old age despite the gradual weakening of the body. He admits that its development is dependent on the data of sense perception, but insists that this is not incompatible with its freedom from the body when fully developed and perfected. As for its being a form of body, not all forms are alike; and it is not so certain that the rational power is a form of body. Neither the difficulties nor the solution are of Ibn Daud's making. They are as old as Aristotle, and his successors grappled with them as best they could.