Although it is thus true that the rational soul is independent of the body, nevertheless it did not exist before the body any more than the lower souls. For if it did, it was either one soul for all men, or there were as many souls as there are individual men. The first is impossible; for the same soul would then be wise and ignorant, good and bad, which is impossible. Nor could the separate souls be different, for being all human souls they cannot differ in essence, which is their common humanity. But neither can they differ in accidental qualities, for simple substances have no accidents. They cannot therefore be either one or many, _i. e._, they cannot be at all before body. Nor must we suppose because the reason exercises its thought functions without the use of a corporeal organ that it appears full fledged in actual perfection in the person of the infant. Experience teaches otherwise. The perfections of the human soul are in the child potential. Later on by divine assistance he acquires the first principles of knowledge about which there is no dispute, such as that two things equal to the same thing are equal to each other, that two contrary predicates cannot apply to the same subject at the same time in the same relation, and so on. Some of these are the fundamental principles of mathematics, others of other sciences. Then he progresses further and learns to make premises and construct syllogisms and argue from the known to the unknown. We have thus three stages in the development of the reason. The first potential stage is known as the _hylic_ or _potential intellect_. The second is known as the _actual intellect_, and the third is the _acquired intellect_. If not for the body the person could not make this progress. For without body there are no senses, and without senses he would not see how the wine in the barrel ferments and increases in volume, which suggests that quantity is accident and body is substance. Nor would he learn the distinction between quality and substance if he did not observe a white garment turning black, or a hot body becoming cold. There is need therefore of the body with its senses to lead to a knowledge of the universals. But this knowledge once acquired, the soul needs not the body for its subsequent existence; and as the soul is not a corporeal power, the death of the body does not cause the extinction of the soul. 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.