Kitap 9
4
And since contrary attributes cannot be induced in the same subject, and science is a potency which depends upon the possession of a rational formula, and the soul contains a principle of motion, it follows that whereas the salutary can only produce health, and the calefactory only heat, and the frigorific only cold, the scientific man can produce both contrary results.
5
For the rational account includes both, though not in the same way; and it is in the soul, which contains a principle of motion, and will therefore, by means of the same principle, set both processes in motion, by linking them with the same rational account. Hence things which have a rational potency produce results contrary to those of things whose potency is irrationalThe meaning of this awkward sentence is clearly shown in the latter part of 4.; for the results of the former are included under one principle, the rational account.
6
It is evident also that whereas the power of merely producing (or suffering) a given effect is implied in the power of producing that effect well , the contrary is not always true; for that which produces an effect well must also produce it, but that which merely produces a given effect does not necessarily produce it well.
