b) The Kantian adoption of the principle of the distinction between the practical and theoretical spheres

This view (morality belongs to the practical sphere, and not to the theoretical one) seems generally admitted -in spite of the rivalry of the Stoic classification that divides knowledge in ethics, logic and physics- until Kant, who takes over most of it.
Thus he presents his moral philosophy in a Critique of Practical Reason. However, he does not act like this for the same reasons as Aristotle. He does not put morality in the practical sphere because of a consideration on the principle of movement or on the degree of certainty of its object, but because of a distinction between what is a matter for our liberty, and what is not.

He distinguishes between the theoretical and practical spheres, as soon as 1770: Something is considered theoretically when we attend only to what belongs to the thing; practically, when we view what by liberty should be in it ¹.
It is in the Critique of Practical Reason that he defines most explicitly this concept: [what] is practical for us, i.e., to be realized by our will ².
So the practical knowledge is that which contains imperatives, and conversely, theoretical cognitions are those which express not what ought to be, but what is; and therefore have as their object not an action but a fact ³.

We see that Kant defines the practical field by the concepts of liberty, will, and imperatives, and not by the Aristotelian motives above mentioned. Nevertheless, the idea remains intact: morality belongs to the practical field.

c) Consequence of this attribution of morality to the practical field

The idea that morality deals with the practical sphere has in a first time led us to attribute to morality some properties related to the notion of praxis.
Praxis is fundamentally action, which is different from what is mistakenly assumed as an action, namely production (poiésis). So one has considered morality as a certain aspect of action. As action is performed by man, one has maintained that morality was the study of a certain characteristic of the human action. From this, one has concluded that to study morals is to study something which concerns action, and something human. The object of morals is the human action.
Thus R. Misrahi proposes this definition of morals: Morals: in the traditional thought, it denotes this part of the philosophy that deals with the search of the best principles of conduct ⁴. By the way, he gives the same meaning to ethics that is the philosophical reflection which defines principles for the conduct of life ⁵, but for this purpose, is considered as a meditation on happiness rather than duty.

The idea that morals concerns action and man seems generally accepted. It is true that Kant affirms that it concerns all reasonable beings, and not only man; but it includes man and this does not contradict the consensus that I try to show. On the other hand, some thinkers have maintained that the object of morals may consist in the character of man, i.e. something which deals with “being”, rather than “doing”; but it is only because we think that this being can influence our action.
So here again, it is fundamentally the human action that is the object of morality (the same analysis can be done if we hold that it is the intention, and not action, that is concerned with morals: in fact it is only because one considers that this intention leads to an action).

What interests us here is to determine to which conception of value this conception of morality has led, indirectly. Since in effect the reflection on value has been made by moral concepts, morality and axiology being confounded, as I have tried to prove, this conception of morality as being classed in the practical field, and not the theoretical one, must have had an impact on the conception of value. The main one being, in my view, that we tend now to see axiology as a practical science, similar to ethics, politics and economy, etc. and not as a theoretical one, similar to mathematics or physics. If we add that, in the contemporary configuration of knowledge, the disciplines studying the human action are the ‘social sciences’, which are opposed to ‘exact sciences’, we may conclude that the vague conception that we spontaneously have consists in classifying it as a social science.

Now we can ask two questions, in understanding their relationship: “Is axiology a practical science or a theoretical one?” and “Is axiology a social science?”.

1. The Form and Principles of the Sensible and Intelligible World, §9, note ; AK I, 396
2. Critique of Practical Reason, Book II, ch. II, I
3. Introduction to Logic, Introduction, Appendix, AK IX, 86-87
4. What is ethics? p. 254
5. Ibid., p. 241