Treatise II. On Conscience

Conscience can be defined: a judgment concerning the honesty or dishonesty of an act to be placed here and now. It is called, 1st, a judgment, for conscience is not some special faculty, but the intellect itself insofar as it actually judges. It is called, 2nd, concerning the honesty or dishonesty of an act, because this judgment does not regard the utility, fittingness, or facility of the act, but only its morality, or its relation of order or deformity to right reason. It is called, 3rd, to be placed here and now, for that judgment regards the action at hand which it ought to direct, but not a past action. Hence conscience differs from synderesis, which is: a habit of first principles concerning things to be done. Cf. St. Thomas, p. 1, q. 79, arts. 12 and 13. - St. Alphonsus, n. 2. - Bouquillon, n. 248.

Conscience is distinguished in many ways, for it is:

1st. Right or erroneous, according as it dictates what is true or false.

2nd. Certain or doubtful, according as the mind firmly judges something to be good or bad, or, on the contrary, remains suspended concerning the honesty of an action.

3rd. Scrupulous or lax, according as, either from an empty motive, it apprehends sin where there is none, or, on the contrary, from a lighter cause, presumes sin to be absent, or holds as light what is grave.

4th. Probable or improbable, according as the mind is inclined to opine from a grave or from a weak motive. Concerning each separately.