Introduction to Classical Ethics, by St. Thomas Aquinas

St. Thomas Aquinas, the model of Scholasticism.
St. Thomas Aquinas (1225-1274)

As the Philosopher says in the beginning of the Metaphysics I.2, “it is the business of the wise man to order”. The reason for this is that wisdom is the most powerful perfection of reason whose characteristic is to know order. Even if the sensitive powers know some things absolutely, nevertheless to know the order of one thing to another is exclusively the work of intellect or reason.

Now a twofold order is found in things. One kind is that of parts of a totality, that is, a group, among themselves, as the parts of a house are mutually ordered to each other. The second order is that of things to an end. This order is of greater importance than the first. For, as the Philosopher says in the eleventh book of the Metaphysics, the order of the parts of an army among themselves exists because of the order of the whole army to the commander.

Now order is related to reason in a fourfold way. There is one order that reason does not establish but only beholds, such is the order of things in nature. There is a second order that reason establishes in its own act of consideration, for example, when it arranges its concepts among themselves, and the signs of concept as well, because words express the meanings of the concepts. There is a third order that reason in deliberating establishes in the operations of the will. There is a fourth order that reason in planning establishes in the external things which it causes, such as a chest and a house.

Because the operation of reason is perfected by habit, according to the different modes of order that reason considers in particular, a differentiation of sciences arises. The function of natural philosophy is to consider the order of things that human reason considers but does not establish-understand that with natural philosophy here we also include metaphysics. The order that reason makes in its own act of consideration pertains to rational philosophy (logic), which properly considers the order of the parts of verbal expression with one another and the order of principles to one another and to their conclusions. The order of voluntary actions pertains to the consideration of moral philosophy. The order that reason in planning establishes in external things arranged by human reason pertains to the mechanical arts.

Accordingly it is proper to moral philosophy, to which our attention is at present directed, to consider human operations insofar as they are ordered one another and to an end.