Objection 1. It would seem that theologians should not take note of the circumstances of human acts. Because theologians do not consider human acts otherwise than according to their quality of good or evil. But it seems that circumstances cannot give quality to human acts; for a thing is never qualified, formally speaking, by that which is outside it; but by that which is in it. Therefore theologians should not take note of the circumstances of acts.
Objection 2. Further, circumstances are the accidents of acts. But one thing may be subject to an infinity of accidents; hence the Philosopher says (Metaph. vi, 2) that "no art or science considers accidental being, except only the art of sophistry." Therefore the theologian has not to consider circumstances.
Objection 3. Further, the consideration of circumstances belongs to the orator. But oratory is not a part of theology. Therefore it is not a theologian's business to consider circumstances.
On the contrary, Ignorance of circumstances causes an act to be involuntary, according to Damascene (De Fide Orth. ii, 24) and Gregory of Nyssa [Nemesius, De Nat. Hom. xxxi.]. But involuntariness excuses from sin, the consideration of which belongs to the theologian. Therefore circumstances also should be considered by the theologian.
I answer that, Circumstances come under the consideration of the theologian, for a threefold reason. First, because the theologian considers human acts, inasmuch as man is thereby directed to Happiness. Now, everything that is directed to an end should be proportionate to that end. But acts are made proportionate to an end by means of a certain commensurateness, which results from the due circumstances. Hence the theologian has to consider the circumstances. Secondly, because the theologian considers human acts according as they are found to be good or evil, better or worse: and this diversity depends on circumstances, as we shall see further on (18, A10,11; 73, 7). Thirdly, because the theologian considers human acts under the aspect of merit and demerit, which is proper to human acts; and for this it is requisite that they be voluntary. Now a human act is deemed to be voluntary or involuntary, according to knowledge or ignorance of circumstances, as stated above (Question 6, Article 8). Therefore the theologian has to consider circumstances.
Reply to Objection 1. Good directed to the end is said to be useful; and this implies some kind of relation: wherefore the Philosopher says (Ethic. i, 6) that "the good in the genus 'relation' is the useful." Now, in the genus "relation" a thing is denominated not only according to that which is inherent in the thing, but also according to that which is extrinsic to it: as may be seen in the expressions "right" and "left," "equal" and "unequal," and such like. Accordingly, since the goodness of acts consists in their utility to the end, nothing hinders their being called good or bad according to their proportion to extrinsic things that are adjacent to them.
Reply to Objection 2. Accidents which are altogether accidental are neglected by every art, by reason of their uncertainty and infinity. But such like accidents are not what we call circumstances; because circumstances although, as stated above (Article 1), they are extrinsic to the act, nevertheless are in a kind of contact with it, by being related to it. Proper accidents, however, come under the consideration of art.
Reply to Objection 3. The consideration of circumstances belongs to the moralist, the politician, and the orator. To the moralist, in so far as with respect to circumstances we find or lose the mean of virtue in human acts and passions. To the politician and to the orator, in so far as circumstances make acts to be worthy of praise or blame, of excuse or indictment. In different ways, however: because where the orator persuades, the politician judges. To the theologian this consideration belongs, in all the aforesaid ways: since to him all the other arts are subservient: for he has to consider virtuous and vicious acts, just as the moralist does; and with the orator and politician he considers acts according as they are deserving of reward or punishment.
Source: Summa Theologica (New Advent)