Why does the fact that moral laws or universal maxims are pure truths of reason imply they are the right or moral thing to do for Kant?

Question

The question is based on an explanation from https://iep.utm.edu/kantview/ which states that what you should do, for Kant, is to "act rationally, in accordance with a universal moral law."

My understanding of Kant is this:

• moral law = universal maxim+

• maxim+ = what you are doing, and the reason why is because it is the right thing to do

• maxim- = what you are doing, and the reason why is for some other reason not related to morals

• What the right thing to do is = maxim+ that everyone can rationally follow and will to be = categorical imperative

• What the wrong thing to do is = maxim+ that everyone cannot rationally follow and will to be

• What you should do for some other reason = maxim- that gets you to the goal you want = hypothetical imperative

• What you should not do for some other reason = maxim- that does not get you to the goal you want

Is this a correct understanding? Is it also true that actions that are morally relevant are the actions that have reasons based on the action considered in and of itself to be good or bad?

But my question would then be: Why does the fact that moral laws or universal maxims are pure truths of reason imply they are the right or moral thing to do? Or, if this is false, what is the justification for the claim that What the right thing to do is = maxim+ that everyone can rationally follow and will to be?

For example: consider the maxim "I will only sometimes lie, but tell the truth most of the time such that others can believe me in almost every circumstance."

I do not see why you could not will this become a universal truth which everyone acts on... But this seems to imply that lying is not bad in of itself; it is only bad if others assume I will lie to them as a result of the universalization. So I do not see the connection between universal truth of reason and the right thing to do. What is the connection Kant makes to justify the implication? Why does a universal maxim/categorical imperative = right thing to do?

Answer 1

Part of the answer lies in Kant's notorious "faculty psychology," a crisp separation of consciousness/mind into compartments that interface in a metaphorically mechanical (AKA "rigorous") way. The conception of the pure will arises from, and for, pure reason, so inasmuch as the faculty of the will appears in the system, it will proceed from first principles of reason, not understanding or sensibility.

Notice that the four kinds of ethical theories (with various indicated subkinds) that Kant addresses as to their flaws, are in counterpoint with the categories of principles of the understanding and their own fourfold heading. The axioms of intuition and anticipations of perception are reflected by appeals to pleasure and emotion, or even a claimed proto-Moorean/Rossian (read: robust/vivid) faculty of deontic intuition proper. Perfectionism and divine sovereignty reflect the analogies of experience (the perfection of action in a substance and its community of substances) and the postulates of empirical thought (to wit, the divine majesty is the interpolant of ultimate necessity).

But for reasons of direction-of-action a priori, this is not how Kant thinks it is to be with respect to the moral law. That is, he can absorb aspects and elements of those other theories into a stronger, more original (in two senses), framework, that of the architectonic of pure reason. The notion of the categorical imperative itself appears specifically as a manifestation of the distinction between categorical and hypothetical judgments in general, modulo Kant's "categorification" of those as substance and causality. Viz., a "practical substance" (read: moral substance) is such that its autonomous action ought to never be a "predicate of" some other action, but all other actions should be predicates of it, and it of itself no less as well. But this is not a private action, but a universal one: that is, one cannot do what is right or good utterly on one's own, but must comport one's will with that of all possible others as well on some level.

Another parallelism: the transcendental ideal of the Transcendental Dialectic is matched by the type of the moral law in the second Critique. Again, then, we see a reflection of a structure/force of pure reason, in deeper moral language; not unexpected, granted, given Kant's definition of "type," but still a perhaps noteworthy moment in the system as such.