My professor said that he believes the primary purpose behind Kant's Critique of Pure Reason is to respond to the empiricist view that morals are ultimately subjective.

He believes that the primary purpose behind Kant's epistemology is to show that through transcendental idealism and through the possibility of synthetic *a priori* knowledge, there is a certain truth that lies within all humans and that there thus must exist "a moral truth."

Is this likely true? And if so, what evidence is there in Kant's CPR to show that his philosophy is indeed primarily about morals?