Objection 2: Further, it is written (Prov.13:16): "The crafty [Douay: 'prudent'] man doth all things with counsel." Therefore, he does so either for a good or for an evil end. If for a good end, there is no sin seemingly, and if for an evil end, it would seem to pertain to carnal or worldly prudence. Therefore craftiness is not a special sin distinct from prudence of the flesh.
Objection 3: Further, Gregory expounding the words of Job 12, "The simplicity of the just man is laughed to scorn," says (Moral. x, 29): "The wisdom of this world is to hide one's thoughts by artifice, to conceal one's meaning by words, to represent error as truth, to make out the truth to be false," and further on he adds: "This prudence is acquired by the young, it is learnt at a price by children." Now the above things seem to belong to craftiness. Therefore craftiness is not distinct from carnal or worldly prudence, and consequently it seems not to be a special sin.
On the contrary, The Apostle says (2 Cor.4:2): "We renounce the hidden things of dishonesty, not walking in craftiness, nor adulterating the word of God." Therefore craftiness is a sin.
I answer that, Prudence is "right reason applied to action," just as science is "right reason applied to knowledge." In speculative matters one may sin against rectitude of knowledge in two ways: in one way when the reason is led to a false conclusion that appears to be true; in another way when the reason proceeds from false premises, that appear to be true, either to a true or to a false conclusion. Even so a sin may be against prudence, through having some resemblance thereto, in two ways. First, when the purpose of the reason is directed to an end which is good not in truth but in appearance, and this pertains to prudence of the flesh; secondly, when, in order to obtain a certain end, whether good or evil, a man uses means that are not true but fictitious and counterfeit, and this belongs to the sin of craftiness. This is consequently a sin opposed to prudence, and distinct from prudence of the flesh.
Reply to Objection 1: As Augustine observes (Contra Julian. iv, 3) just as prudence is sometimes improperly taken in a bad sense, so is craftiness sometimes taken in a good sense, and this on account of their mutual resemblance. Properly speaking, however, craftiness is taken in a bad sense, as the Philosopher states in Ethic. vi, 12.
Reply to Objection 2: Craftiness can take counsel both for a good end and for an evil end: nor should a good end be pursued by means that are false and counterfeit but by such as are true. Hence craftiness is a sin if it be directed to a good end.
Reply to Objection 3: Under "worldly prudence" Gregory included everything that can pertain to false prudence, so that it comprises craftiness also.