In the beginning of his Metaphysics, Aristotle states that the human race lives by art and reasoning. He seems to touch here on something properly human, which distinguishes man from the other animals. For while the brute animals are moved to their actions by natural instinct, we direct our actions by rational judgments. To enable us to carry out these actions easily and in an orderly way, we have invented many arts. For an art is nothing other than a certain ordering of reason by which human acts achieve a suitable end through determinate means.
Now reason is able to direct not only the acts of inferior faculties, but also its own acts. For the capacity to reflect upon itself is proper to the intellectual power; the intellect understands itself and, similarly, reason can reason about itself. Now, if by reasoning about the acts of the hand, we discovered building, and this art enables us to build easily and in an orderly way, then, for the same reason, we need an art to direct the acts of reason, so that in these acts also we may proceed in an orderly way, easily, and without error. This art is logic, the science of reason.
[St. Thomas Aquinas, Commentary on Aristotle's Posterior Analytics, Berquist, tr., Dumb Ox Books (Notre Dame, IN: 2007) p. 1.]
