Objection 1. It would seem that the will is not moved by a passion of the sensitive appetite. For no passive power is moved except by its object. Now the will is a power both passive and active, inasmuch as it is mover and moved, as the Philosopher says of the appetitive power in general (De Anima iii, text. 54). Since therefore the object of the will is not a passion of the sensitive appetite, but good defined by the reason, it seems that a passion of the sensitive appetite does not move the will.
Objection 2. Further, the higher mover is not moved by the lower; thus the soul is not moved by the body. Now the will, which is the rational appetite, is compared to the sensitive appetite, as a higher mover to a lower: for the Philosopher says (De Anima iii, text. 57) that "the rational appetite moves the sensitive appetite, even as, in the heavenly bodies, one sphere moves another." Therefore the will cannot be moved by a passion of the sensitive appetite.
Objection 3. Further, nothing immaterial can be moved by that which is material. Now the will is an immaterial power, because it does not use a corporeal organ, since it is in the reason, as stated in De Anima iii, text. 42: whereas the sensitive appetite is a material force, since it is seated in an organ of the body. Therefore a passion of the sensitive appetite cannot move the intellective appetite.
On the contrary, It is written (Daniel 13:56): "Lust hath perverted thy heart."
I answer that, A passion of the sensitive appetite cannot draw or move the will directly; but it can do so indirectly, and this in two ways. First, by a kind of distraction: because, since all the soul's powers are rooted in the one essence of the soul, it follows of necessity that, when one power is intent in its act, another power becomes remiss, or is even altogether impeded, in its act, both because all energy is weakened through being divided, so that, on the contrary, through being centered on one thing, it is less able to be directed to several; and because, in the operations of the soul, a certain attention is requisite, and if this be closely fixed on one thing, less attention is given to another. In this way, by a kind of distraction, when the movement of the sensitive appetite is enforced in respect of any passion whatever, the proper movement of the rational appetite or will must, of necessity, become remiss or altogether impeded.
Secondly, this may happen on the part of the will's object, which is good apprehended by reason. Because the judgment and apprehension of reason is impeded on account of a vehement and inordinate apprehension of the imagination and judgment of the estimative power, as appears in those who are out of their mind. Now it is evident that the apprehension of the imagination and the judgment of the estimative power follow the passion of the sensitive appetite, even as the verdict of the taste follows the disposition of the tongue: for which reason we observe that those who are in some kind of passion, do not easily turn their imagination away from the object of their emotion, the result being that the judgment of the reason often follows the passion of the sensitive appetite, and consequently the will's movement follows it also, since it has a natural inclination always to follow the judgment of the reason.
Reply to Objection 1. Although the passion of the sensitive appetite is not the direct object of the will, yet it occasions a certain change in the judgment about the object of the will, as stated.
Reply to Objection 2. The higher mover is not directly moved by the lower; but, in a manner, it can be moved by it indirectly, as stated.
The Third Objection is solved in like manner.
Source: Summa Theologica (New Advent)