Kant's Critique of Pure Reason
II. TRANSCENDENTAL DOCTRINE OF METHOD
Chapter 2: THE CANON OF PURE REASON (p. 629)
Canon: the sum total of the a priori principles of the correct employment of certain faculties of knowledge.
The Transcendental Analytic is the canon of the pure understanding.
There is no canon of pure reason in its speculative employment because it cannot produce synthetic knowledge.
The greatest and perhaps sole use of pure reason in its speculative employment is only negative; since it serves not as an organon for the extension, but as a discipline for the limitation of pure reason, and, instead of discovering truth, it has only the modest merit of guarding against error.
If there be any correct employment of pure reason, in which case there must be a canon of its employment, the canon will deal with the practical employment of reason.
In respect of all three the merely speculative interest of reason is very small because they would not be of any use in the study of nature.
These three propositions are for speculative reason always transcendent and allow of no immanent employment - that is, employment in reference to objects of experience.
If these propositions are not necessary for knowledge, their importance must concern only the practical.
The Practical: everything that is possible through freedom.
When the conditions of the exercise of our free will are empirical, reason can supply none but pragmatic laws of free action for the attainment of those ends which are commended to us by the senses (happiness).
Moral Laws: Pure Practical Laws, whose end is given through reason completely a priori and which are not prescribed to us in an empirically conditioned but in an absolute manner.
Belong to the practical employment of reason.
They refer to something further, namely, to the problem of what we ought to do, if the will is free, if there is a God and a future world.
Freewill: a will which can be determined independently of sensuous impulses.
Opposed to animal will which can be determined only through sensuous impulses.
Everything which is bound up with freewill, whether as a ground or a consequence, is entitled practical.
All practical concepts relate the objects of satisfaction and dissatisfaction (pleasure and pain), and therefore, at least indirectly to the object of our feelings. But feeling is not a faculty whereby we represent things, so our judgments so far as they relate to pleasure or pain do not belong to transcendental philosophy.
Practical freedom can be proved through experience.
We have the power to overcome impressions of our faculty of sensuous desire, by calling up representations of what, in a more indirect manner, is useful or injurious.
These considerations are based on reason.
These laws, which reason provides, are imperatives, that is, objective laws of freedom, which tell us what ought to happen.
Opposed to the laws of nature which relate only to that which happens.
These laws are therefore entitled practical laws.
While we thus know practical freedom to be one of the causes in nature, namely to be a causality of reason in the determination of the will, transcendental freedom demands the independence of this reason from all determining causes of the sensible world.
Transcendental freedom is thus, it would seem, contrary to the law of nature, and therefore to all possible experience, and so remains a problem.
This problem does not come within the province of reason in its practical employment so we can leave it aside.
Therefore the canon of pure reason only deals with two questions, which relate to the practical interest of pure reason: is there a God, and is there a future life.