The meaning of what is said is according to the motive for saying it: because things are not subject to speech, but speech to things. Therefore we should take account of the motive of the lawgiver, rather than of his very words.
Thomas AquinasGiven the sin of impiety through which they [the Romans] sinned against the divine nature [by idolatry], the punishment that led them to sin against their own nature followed.... I say, therefore, that since they changed into lies [by idolatry] the truth about God, He brought them to ignominious passions, that is, to sins against nature; not that God led them to evil, but only that he abandoned them to evil.
Thomas AquinasFor although the will cannot be inwardly moved by any creature, yet it can be moved inwardly by God.
Thomas AquinasBecause of the diverse conditions of humans, it happens that some acts are virtuous to some people, as appropriate and suitable to them, while the same acts are immoral for others, as inappropriate to them.
Thomas AquinasEvil denotes the lack of good. Not every absence of good is an evil, for absence may be taken either in a purely negative or in aprivative sense. Mere negation does not display the character of evil, otherwise nonexistents would be evil and moreover, a thing would be evil for not possessing the goodness of something else, which would mean that man is bad for not having the strength of a lion or the speed of a wild goat. But what is evil is privation; in this sense blindness means the privation of sight.
Thomas Aquinas