What is the main idea of Kant’s transcendental philosophy and Copernican Revolution? The Kantian transcendentalism is the first theory of experience related to the solution of the semantic problem set in his letter to M. Hertz (02.21.1772) about the ground of the relation of our [a priori] representation to the object. There are two ways to solve it: realism (the empirical vector from the real things/objects to representations) and constructivism (the vector from the a priori form (or ‘representations’) to the objects). But Kantian transcendental idealism is not constructivism, because Kant keeps the empirical (realistic) vector by affixing our sensibility with things/objects and says that his theory of experience is an empirical realism. The Kantian transcendentalism as altered method of human thinking in metaphysics is associated with the splitting of the thing/object into the actual/real object (Kantian thing-in-itself) and object of experience (Kantian appearance), that mediate the relationship between things and representations, or the transcendental triad «object (thing-in-itself) — appearance — representation». Unlike modern epistemic constructivism as a procedure for constructing objects, Kant develops transcendental constructivism in mathematics as cognition through construction of concepts in intuition, i.e. constructivism regarding appearances, but not things–in–themselves.