Philosophy seems to consist of two parts, Logic and Metaphysics. I exclude Ethics, for two reasons. In the first place, as the science of the end and aim of life, [ethics] seems to be exclusively psychical, and therefore to be confined to a special department of experience, while philosophy studies experience in its universal characteristics. In the second place, in seeking to define the proper aim of life, ethics seems to me to rank with the arts, or rather with the theories of the arts, which of all theoretical sciences I regard as the most concrete, while what I mean by philosophy is the most abstract of all the real sciences.
Normative science has three widely separated divisions: i. Esthetics; ii. Ethics; iii. Logic.
… Ethics, or the science of right and wrong, must appeal to Esthetics for aid in determining the summum bonum. It is the theory of self-controlled, or deliberate, conduct.
…it is generally said that the three normative sciences are logic, ethics, and esthetics, being the three doctrines that distinguish good and bad; Logic in regard to representations of truth, Ethics in regard to efforts of will, and Esthetics in objects considered simply in their presentation.
Supposing, however, that normative science divides into esthetics, ethics, and logic, then it is easily perceived, from my standpoint, that this division is governed by the three categories. For Normative Science in general being the science of the laws of conformity of things to ends, esthetics considers those things whose ends are to embody qualities of feeling, ethics those things whose ends lie in action, and logic those things whose end is to represent something.
Ethics is that normative science which studies the conditions of that excellence which may or may not belong to voluntary action in its relation to its purpose.
…What quality of anything is it that is fine in itself without any ulterior reason? Then the problem of ethics being the study of the general conditions for making the fine existent, it is quite plausible in advance that this may depend upon what the fine is. But it is a part of the solution of that problem that the chief agency for the actualization of the fine must be the action of self-control. As soon, therefore, as we come to see Reasoning, the primary, and indeed the principal, subject of logic, is precisely self-controlled thought, the applicability to it of ethical theory becomes credible, to say the least.
Reasoning is self-controlled thought; and thus Logic is directly dependent upon Ethics, or the science of self-control, in general.