“[A]ll moral philosophy rests entirely on its pure part and, applied to the human being, it does not borrow the least thing from our acquaintance with him [...] but gives him, as a rational being, laws a priori; which of course still require a power of judgment sharpened by experience, partly to distinguish in what cases they are applicable [...]”

Here, Kant describes how moral philosophy must balance empiricism and rationality. While empirical thought cannot be the basis for a far-reaching metaphysics of morals, individuals can use their own experiences to determine when moral laws ought to be applied. However, rational, a priori laws allow humans to conceive morality in the first place.

“A metaphysics of morals is thus indispensably necessary, not merely on the grounds of speculation, for investigating the source of the practical principles that lie a priori in our reason, but because morals themselves remain subject to all sorts of corruption as long as we lack that guideline and supreme norm by which to judge them correctly.”

Kant argues that a metaphysics of morals prevents corruption. Establishing one will be of practical significance. This allows the reader to see how Kant’s ideas could function in everyday life.

“The present groundwork, however, is nothing more than the identification and corroboration of the supreme principle of morality, which by itself constitutes a business that is complete in its purpose and to be separated from every other moral investigation.”

This quote comes after Kant admits he will be unable to prove a metaphysics of morals in this work. However, by proving the presence of the supreme principle of morality, he will be able to pursue this in the future. The presence of this principle could also inspire other philosophers to continue Kant’s work.