Critique of Practical Reason

Critique of Practical Reason

1788 German edition
Author	Immanuel Kant
Original title	Critik a der praktischen Vernunft
Translator	Thomas Kingsmill Abbott
Language	German
Subject	Moral and ethical philosophy
Published	1788
Media type	Print
Preceded by	Critique of Pure Reason
Followed by	Critique of Judgment
aKritik in modern German.

The Critique of Practical Reason (German: Kritik der praktischen Vernunft, KpV) is the second of Immanuel Kant's three critiques, first published in 1788. It follows on from Kant's Critique of Pure Reason and deals with his moral philosophy.

The second Critique exercised a decisive influence over the subsequent development of the field of ethics and moral philosophy, beginning with Johann Gottlieb Fichte's Doctrine of Science and becoming, during the 20th century, the principal reference point for deontological moral philosophy.

Kant sketches out here what is to follow. Most of these two chapters focus on comparing the situation of theoretical and of practical reason and therefore discusses how the Critique of Practical Reason compares to the Critique of Pure Reason.

The first Critique was a critique of the pretensions of pure theoretical reason to attain metaphysical truths beyond the ken of applied theoretical reason. The conclusion was that pure theoretical reason must be restrained, because it produces confused arguments when applied outside of its appropriate sphere. However, the Critique of Practical Reason is not a critique of pure practical reason, but rather a defense of it as being capable of grounding behavior superior to that grounded by desire-based practical reasoning. It is actually a critique, then, of the pretensions of applied practical reason. Pure practical reason must not be restrained, in fact, but cultivated.

Kant informs us that while the first Critique suggested that God, freedom, and immortality are unknowable, the second Critique will mitigate this claim. Freedom is indeed knowable because it is revealed by God. God and immortality are also knowable, but practical reason now requires belief in these postulates of reason. Kant once again invites his dissatisfied critics to actually provide a proof of God's existence and shows that this is impossible because the various arguments (ontological, cosmological and teleological) for God's existence all depend essentially on the idea that existence is a predicate inherent to the concepts to which it is applied.