Our conclusion then is that prudence is a formed faculty which apprehends truth by reasoning or calculation, and issues in action, in the field of human good.

Moreover, art [or the artistic faculty] has its excellence [or perfect development] in something other than itself, but this is not so with prudence. Again, in the domain of art voluntary error is not so bad as involuntary, but it is worse in the case of prudence, as it is in the case of all the virtues or excellences. It is plain, then, that prudence is a virtue or excellence, and not an art.

And the rational parts of the soul or the intellectual faculties being two in number, prudence will be the virtue of the second, [the calculative part or] the faculty of opinion; for opinion deals with that which is variable, and so does prudence.

But it is something more than “a formed faculty of apprehending truth by reasoning or calculation;” as we see from the fact that such a faculty may be lost, but prudence, once acquired, can never be lost. 146