From a mountain, a river flowed down, gradually dividing into channels. One of these channels ended at the perimeter of three fields. The owner of the first field planted and sowed the seeds, but did nothing to use the channel that ran along one side of his field to irrigate it, and as a result, the seeds he had sown dried up.
The owner of the second field also sowed his field, but he watered it so constantly that the seeds drowned in the water, and the tiny roots that began to sprout rotted. The third also sowed seed and watered it according to the needs of the field and the seed, and he was able to harvest fruit from them.
The difference between these three owners is prudence, and more specifically, one of the integral parts of prudence, which is reason. As St. Thomas explains, reason is necessary for prudence because to be prudent, a man must reason well.
In prudence, “more than in any other virtue, man needs to have good reasoning in order to be able to apply universal principles to particular cases which are varied and uncertain” (II-II, 49, 5 ad 2). Following the example of the story, it is not only necessary to know that plants need water, but also to know how much water they need, which depends on the field and the kind of plant.
Many things can impede the use of reason in our actions, thus making them imprudent actions. As was shown in the case of the first owner (and what happens in most cases), it could be a disordered passion that is an obstacle to the use of our reason; perhaps it is because of laziness, as was likely the motive of the first owner in the story, or some other disordered passion, that prevents us either from reasoning well, or even from reasoning at all, so as not to do what is prudent.
As illustrated by the second case in the story, it could also be that our reasoning is not good and so it is necessary to grow in the virtue of prudence, because it is precisely the virtue of prudence that makes us think and reason well. So, reasoning well is a part of prudence, and to the extent that we grow in this virtue, we will grow also in our reasoning, because the rest of the integral parts of prudence, especially the cognitive ones, help us to reason well.
