Chapter 32 — Part III: The Decalogue — The Ninth and Tenth Commandments
Section 12. Concupiscence, then, is a certain commotion and impulse of the soul, urging men to the desire of pleasures, which they do not actually enjoy. As the other propensities of the soul are not always sinful, neither is the impulse of concupiscence always vicious. It is not, for instance, sinful to desire food and drink; when cold, to wish for warmth; when warm, to wish to become cool. This lawful species of concupiscence was implanted in us by the Author of nature; but in consequence of the sin of our first parents it passed the limits prescribed by nature and became so depraved that it frequently excites to the desire of those things which conflict with the spirit and reason.