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

This idea, which places morality in the practical, rather than the theoretical, sphere, seems to be generally accepted, despite the competition from the Stoic tripartition, which divides knowledge into ethics, logic and physics, right up to Kant, who seems to have taken up the essence of it.
He presents his moral philosophy in the Critique of Practical Reason. However, he does not proceed in this way for the same reasons as Aristotle. He does not place morality in the practical sphere because of a consideration of the principle of movement or the degree of certainty of its object, but on the basis of a distinction between what comes under our freedom and what does not.

He distinguished between the theoretical and practical spheres as early 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 this concept most explicitly: [what] is practical for us, i.e., to be realized by our will ².
Practical knowledge is therefore that which contains imperatives, whereas 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.

So it is on the basis of the concepts of freedom, will and imperatives that Kant defines the practical field, and no longer on the basis of the Aristotelian motives we have just mentioned. Nevertheless, the idea remains intact: morality belongs to the practical field.

c) The consequence of attributing morality to the practical sphere

The idea that morality belongs to the practical sphere has, in our view, led thought to attribute to morality certain characteristics that are linked to the notion of praxis.
First of all, praxis is fundamentally action, which differs from what might be mistaken for action, namely production (poiésis). This has led us to consider morality as the study of a certain aspect of action. Since this action is performed by us, this led to morality being seen as the study of a certain character of human action. From this, it was concluded that to study morality was to study something to do with action, and something human. The object of morality is therefore human action.
R. Misrahi, for example, offers this definition of morality: Morality: in traditional thought, designates the part of philosophy devoted to the search for the best principles of conduct ⁴. He gives the same meaning to ethics, which is the philosophical reflection that sets out to define principles for the conduct of life ⁵ but which, for the purposes of this research, is more a meditation on happiness than on our duty.

This idea, according to which morality concerns action and human beings, seems to be generally adopted. Kant, it is true, asserts that morality concerns every reasonable being, not just humans; but this includes humans and therefore does not contradict the consensus we are trying to identify. On the other hand, some thinkers have defended the idea that the object of morality might lie rather in human's character, in other words in something that has more to do with "being" than with "doing"; but this is only because we attribute to this "being" a capacity to influence our action.
So it is always, fundamentally, human action that is the object of morality (the same analysis can be made if we maintain that it is in intention, and not action, that morality resides: morality is considered as such only because it gives rise to action).

What interests us here is to determine what conception of value may have led, indirectly, to this conception of morality. Since, as we have tried to show, the conception of value has taken place in and through morality, with morality absorbing axiology, this conception of morality as belonging to the practical rather than the theoretical field must have had repercussions on the conception of value.

The main one, in my opinion, is that there is now a tendency to see axiology as a practical science, akin to ethics, politics and economics, etc., and not as a theoretical science, akin to mathematics or physics. If we add that, in the contemporary configuration of knowledge, the disciplines that study human action are the "human sciences", which are contrasted with the "exact" sciences, then we may think that the vague conception of axiology that spontaneously comes to mind consists in classifying it among the human sciences.

We can then ask ourselves two related questions: "Is axiology a practical or theoretical science?" and "Is axiology a human 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. Qu’est-ce que l’éthique ? p. 254
5. Ibid., p. 241