Summary

In Immanuel Kant's "Critique of Practical Reason," Abbott's translation presents a profound exploration of moral philosophy, distinguishing between speculative and practical reason. Kant argues for the existence of pure practical reason, which doesn't require empirical validation but proves itself through action. This pure reason establishes transcendental freedom, a concept necessary for escaping the antinomy of causality. Freedom, proven by an apodeictic law, becomes the cornerstone for the concepts of God and immortality, providing them with consistence and objective reality.

The work delves into the ideas of freedom, God, and immortality, examining their possibility and necessity within the framework of practical reason. Kant posits that while speculative reason can only conceive of freedom problematically, practical reason demonstrates its reality through moral law. This law serves as the ratio cognoscendi of freedom, while freedom is the ratio essendi of the moral law. The critique addresses the apparent inconsistency between denying objective reality to the supersensible in speculation and admitting it in practical reason, clarifying that practical use doesn't extend theoretical knowledge but establishes the object's belonging through necessary determination of the will a priori.

Kant contrasts autonomy and heteronomy of the will, asserting that the former is the sole principle of moral laws. He criticizes material practical principles, which he argues are based on self-love and private happiness, thus belonging to the lower desires. True morality, according to Kant, arises when reason determines the will through the mere form of the practical rule, independent of any feeling. He introduces the concept of the 'fact of reason,' the consciousness of the fundamental moral law, which is not derived from experience but forces itself upon us as a synthetic a priori proposition. This law, applicable to all rational beings, dictates that one should act so that the maxim of their will can always hold good as a principle of universal legislation.

The book explains how pure reason can be practical and can determine the will independently of empirical elements. This is achieved through the autonomy of the will, demonstrated in the fundamental principle of morality. Freedom and the unconditional practical law are reciprocally implied, with the moral law leading to the concept of freedom. Kant explores the concepts of good and evil, defining them as objects necessarily desired or shunned according to a principle of reason. He distinguishes between das Gute (good) and das Wohl (well), asserting that only the manner of acting, the maxim of the will, can be absolutely good or evil.

The Analytic of Pure Practical Reason demonstrates that pure reason can be practical, determining the will independently of empirical elements, which is proved by the fundamental principle of morality. Kant also address key components such as; the 'Typic of Pure Practical Judgement' where the sensible world is used as the type of a supersensible system of things, the 'Motives of Pure Practical Reason' where moral worth is determined by moral law. The work concludes with a discussion on the postulates of pure practical reason - immortality of the soul and the existence of God. Practical reason asserts objective reality to those concepts of freedom, immorality, and the existence of God.