Since the forms of perception and thought are due to the structure of the knower; it follows that they can give no knowledge of things- in- themselves (noumena) beyond experience. Knowledge is of phenomena; noumena may in a sense be thought, but not known. We cannot discuss the nature of the soul except in terms of its manifestations in empirical psychology. Nor can we talk about the material world in transcendent terms, terms referring beyond our possible experience. If we try to do so, we get in to antinomies. We think the world must have had a beginning, and also that it could not have had one; that matter must be infinitely divisible, but that it cannot be; that there must be causality, but also that there must be freedom; that there must be a Necessary Being, but that we can never find one in experience.
Furthermore, Kant continued, when we try to prove the existence of God by the ontological argument (a necessary being), the cosmological (first cause), or the physico-theological (from universal order). We find there are unwarranted assumptions in each case. The soul, the universe, and God are regulative, not constitutive, ideas. They enable us to organize experience and give it unity; but we cannot establish their validity beyond this. Theoretical (or scientific) reason is thus limited to ” objects of possible experience’.
The question’ what ought I to do?’ Was more fully analyzed in Kant’s Foundations of the Metaphysic of Morals (1785) and in his Critique of Practical Reason (1788). Morality is concerned with the conditions of the highest meaning of conduct, as science and philosophy are concerned with knowledge. In both cases,
According to Kant, the final goal is to bringmatters under the highest possible principles. Morality consists of actions in accordance with principles. An unprincipled man is an immoral man. And the principle here as in science is the principle of consistency, necessity, and universality. It is formulated in the statement,’ So act that the maxim of thy deed may stand as universal law’ That is, follow a rule that every other person may also follow, and ask no special privileges. Grant to others all the rights you claim for yourself. This is practical or moral reason, and since man is the rational animal the meaning may be stated in the form: Respect as ultimate the humanity of every man. Never regard humanity as a means to something else, but always as the final end. The particular rules of conduct, such as the commands of the Decalogue, are specific modes of carrying out the general law.
As Kant developed the theory. Morality is concerned with what ought to be, not with what is; it cannot be derived from a description of human behavior. It is prescriptive, not descriptive. It must therefore be a priori, not a posteriori. And the moral value of all life cannot be measured by its everyday success; it must be measured by its degree of embodiment of principle. A life lived according it principle is good regardless of material success or failure. Ultimately, the only good thing in the world is a good will. Duty is the key word, not pleasure, and the imperative call of duty is categorical, not conditional.
Morality presupposes certain postulates of practical reason. Above all, freedom is assumed (regardless of all the difficulties with the conception that arose in Kant’s Critique of Pure Reason). Without it there would be no meaning to praise and blame, in fact no possibility of such a distinction.
In Nature, too, there is a unity, says Kant, which holds all things together and which is analogous to the unity of art. This gives Nature apparent design, lends it beauty, and suggests the teleological argument for the existence of God.
But our religious life remains subject to the limitations of our experience, according to Kant. Its emphasis must necessarily, then, be upon ethics rather than upon transcendent theology, as he explained in Religion within the limits of Mere Reason (1794).
In his Prolegomena to Any Future Metaphysic, Kant states the three fundamental questions of human interest-” What con I know? What ought I to do? What may I hope?”- And, developing the first question more technically, possible? How is pure physics possible? How far is metaphysics possible? All of these are phases of this central problem: “How are priori synthetic judgments possible? i.e., universal judgments which add to our knowledge and are necessary truths, but the validity of which cannot be established by experience. The reply: such judgments do not anticipate the specific contents of experience, only its general forms.