I answer that, As we have already stated (A. 1) the word “passion” implies that the patient is drawn to that which belongs to the agent.  Now the soul is drawn to a thing by the appetitive power rather than by the apprehensive power:  because the soul has, through its appetitive power, an order to things as they are in themselves:  hence the Philosopher says (Metaph. vi, 4) that “good and evil,” i.e. the objects of the appetitive power, “are in things themselves.”  On the other hand the apprehensive power is not drawn to a thing, as it is in itself; but knows it by reason of an “intention” of the thing, which “intention” it has in itself, or receives in its own way.  Hence we find it stated (Metaph. vi, 4) that “the true and the false,” which pertain to knowledge, “are not in things, but in the mind.”  Consequently it is evident that the nature of passion is consistent with the appetitive, rather than with the apprehensive part.

Reply Obj. 1:  In things relating to perfection the case is the opposite, in comparison to things that pertain to defect.  Because in things relating to perfection, intensity is in proportion to the approach to one first principle; to which the nearer a thing approaches, the more intense it is.  Thus the intensity of a thing possessed of light depends on its approach to something endowed with light in a supreme degree, to which the nearer a thing approaches the more light it possesses.  But in things that relate to defect, intensity depends, not on approach to something supreme, but [o]n receding from that which is perfect; because therein consists the very notion of privation and defect.  Wherefore the less a thing recedes from that which stands first, the less intense it is:  and the result is that at first we always find some small defect, which afterwards increases as it goes on.  Now passion pertains to defect, because it belongs to a thing according as it is in potentiality.  Wherefore in those things that approach to the Supreme Perfection, i.e. to God, there is but little potentiality and passion:  while in other things, consequently, there is more.  Hence also, in the supreme, i.e. the apprehensive, power of the soul, passion is found less than in the other powers.

Reply Obj. 2:  The appetitive power is said to be more active, because it is, more than the apprehensive power, the principle of the exterior action:  and this for the same reason that it is more passive, namely, its being related to things as existing in themselves:  since it is through the external action that we come into contact with things.

Reply Obj. 3:  As stated in the First Part (Q. 78, A. 3) the organs of the soul can be changed in two ways.  First, by a spiritual change, in respect of which the organ receives an “intention” of the object.  And this is essential to the act of the sensitive apprehension:  thus is the eye changed by the object visible, not by being colored, but by receiving an intention of color.  But the