The Instructor 1.13.101

Everything contrary to right reason is sin. The philosophers, for instance, think fit to define the most general passions in this way: desire as an appetite disobedient to reason; fear as an aversion disobedient to reason; pleasure as an elation of the soul disobedient to reason; grief as a contraction of the soul disobedient to reason. If, then, disobedience to reason begets sin, how can obedience to the Word, which we call faith, not necessarily produce what is called duty? For virtue itself is a disposition of the soul in harmony with reason throughout the whole of life. Indeed, most important of all, they define philosophy itself as the cultivation of right reason; so that everything done amiss necessarily arises through a failure of reason, and is rightly called sin (hamartēma, “missing the mark”).