 Wherefore the first practical principles, bestowed on us by nature, do not belong to a special power, but to a special natural habit, which we call “synderesis”. Whence “synderesis” is said to incite to good, and to murmur at evil, inasmuch as through first principles we proceed to discover, and judge of what we have discovered. It is therefore clear that “synderesis” is not a power, but a natural habit. (Summa theologica I, q. 79, a. 12, corp.)