Critique of Practical Reason

1. Practical Reason as the Foundation of Morality

It has merely to show that there is pure practical reason, and for this purpose it criticizes reason’s entire practical faculty.

Critique of Practical Reason. Kant's Critique of Practical Reason aims to demonstrate the existence and nature of pure practical reason, which is the capacity of reason to determine the will independently of empirical influences. This contrasts with theoretical reason, which is concerned with knowledge of objects. Kant argues that morality is grounded in practical reason, not in feelings, inclinations, or external authorities.

Pure vs. Empirical Reason. The central question is whether pure reason alone can determine the will, or whether reason is always conditioned by empirical factors. Kant seeks to establish that pure reason can indeed be practical, providing objective and universal moral laws. This involves a critique of reason's entire practical faculty to prevent empirical reason from claiming exclusive authority.

Objective vs. Subjective Principles. Practical principles can be subjective (maxims) or objective (laws). Maxims are valid only for an individual's will, while laws are universally binding on all rational beings. Kant's goal is to identify the objective practical laws that stem from pure reason and form the basis of morality.

2. The Moral Law as a Fact of Reason

On reflection we do accept the moral law as an authoritative standard of conduct that provides sufficient and overriding reasons for action and we are motivated to act by our judgments of what it requires.

The Moral Law. Kant posits the moral law as a "fact of reason," meaning it is a fundamental principle that we recognize through our moral consciousness. This law is not derived from experience or external sources but is inherent in our rational nature. It serves as an authoritative standard for evaluating actions and motives.

Categorical Imperative. The moral law is expressed through the Categorical Imperative, which commands us to act only according to maxims that we could will to become universal laws. This principle emphasizes the importance of universalizability and consistency in moral decision-making. It is a formal principle, focusing on the form of the maxim rather than its content.

Duty and Motivation. The moral law provides sufficient and overriding reasons for action, even when it conflicts with our desires or interests. We are motivated to act by our judgments of what the moral law requires, recognizing that we can do something simply because it is our duty. This sense of duty is a key aspect of Kant's moral theory.

3. Freedom and the Moral Law: Reciprocal Conditions

Whereas freedom is indeed the ratio essendi of the moral law, the moral law is the ratio cognoscendi of freedom.

Freedom and Morality. Kant argues that freedom and the moral law are reciprocally related. Freedom is the ratio essendi (the ground of being) of the moral law, meaning that the moral law is possible only because we are free. Conversely, the moral law is the ratio cognoscendi (the ground of knowing) of freedom, meaning that we become aware of our freedom through our consciousness of the moral law.

Transcendental Freedom. Kant distinguishes between transcendental freedom (independence from empirical conditions) and psychological freedom (acting according to internal desires). The moral law reveals our transcendental freedom by demonstrating our ability to act independently of our inclinations. This ability is essential for moral responsibility.

The Moral Law Reveals Freedom. In the Critique of Practical Reason, Kant reverses the order of justification from the Groundwork. Here, the authority of the moral law reveals our freedom, rather than the other way around. Our recognition of the moral law as binding upon us discloses our capacity for spontaneous activity, which is the essence of transcendental freedom.

4. Autonomy vs. Heteronomy: The Source of Moral Principles

Only a formal law, that is, one that prescribes to reason nothing more than the form of its universal lawgiving as the supreme condition of maxims, can be a priori a determining ground of the will.

Autonomy of the Will. Autonomy means self-governance or self-legislation. Kant argues that the moral law is a principle of autonomy because it originates from our own reason and is not imposed upon us by external authorities or desires. When we act autonomously, we are bound only to our own fundamental principle.

Heteronomy of the Will. Heteronomy, on the other hand, means being governed by external forces or desires. Kant rejects heteronomous moral theories that base morality on happiness, perfection, or the will of God. These theories fail to establish the unconditional authority of moral principles because they rely on contingent factors.

The Moral Law and Autonomy. The moral law demands that we base our reasons on the legislative form of our maxims, in abstraction from their matter. In acting from this principle, we are guided by the will's own principle and are subject only to the authority inherent in our reason. This is the essence of autonomy.

5. The Highest Good: Virtue and Happiness Combined

The moral law generates a duty to do all we can to bring about the highest good in the world, which he specifies as a state of affairs in which all agents have achieved virtue and happiness is distributed in accordance with virtue.

The Highest Good. The highest good is the complete object of pure practical reason, representing the state of affairs in which virtue and happiness are perfectly combined. It is not merely the sum of virtue and happiness but a state where happiness is distributed in proportion to virtue. This concept serves as a guiding ideal for moral action.

Virtue as the Supreme Condition. Virtue is the supreme condition of the highest good, meaning that it is the necessary prerequisite for happiness. However, virtue alone does not guarantee happiness in the sensible world. The connection between virtue and happiness is not analytic but synthetic, requiring a further condition for its realization.

The Antinomy of Practical Reason. The pursuit of the highest good leads to an antinomy, or contradiction, within practical reason. On the one hand, we have a duty to promote the highest good. On the other hand, our experience suggests that virtue and happiness are not necessarily connected in the world. This antinomy requires a resolution.

6. Postulates of Practical Reason: God and Immortality

As with the idea of freedom, practical reason, in grounding the postulates, resolves questions that reason in its theoretical use raises, but cannot answer.

Postulates of Practical Reason. To resolve the antinomy of practical reason, Kant introduces the postulates of immortality and the existence of God. These postulates are not theoretical claims but practical necessities, required to make sense of our moral experience. They are conditions of the practical possibility of the highest good.

Immortality of the Soul. The postulate of immortality is necessary because the complete conformity of the will with the moral law (holiness) is unattainable in this life. It requires an endless progress toward perfection, which is possible only if the soul continues to exist indefinitely.

Existence of God. The postulate of the existence of God is necessary to ensure that happiness is distributed in proportion to virtue. Since the moral law does not guarantee happiness in the natural world, we must assume a moral author of the universe who can bring about this connection. God is the guarantor of the highest good.

7. The Primacy of Practical Reason: Faith and Knowledge

When we find that reason in its practical use needs to assert certain propositions that were transcendent for theoretical reason, the question arises as to which use of reason has primacy.

Primacy of Practical Reason. Kant argues for the primacy of practical reason over speculative reason. This means that when practical reason needs to assume certain propositions that are beyond the reach of theoretical reason, it is reasonable to accept those propositions. This primacy is based on the unconditional demands of morality.

Rational Faith. The postulates of practical reason constitute a "rational faith" or "reasonable faith," which is distinct from theoretical knowledge. These postulates are not based on empirical evidence or logical proof but on the necessary conditions for the possibility of morality. They provide a basis for assuming the reality of certain metaphysical ideas.

Limits of Knowledge, Room for Faith. Kant famously stated that he "had to deny knowledge in order to make room for faith." This means that by limiting the scope of theoretical reason, he created space for practical reason to assert its claims. The postulates of practical reason do not extend theoretical knowledge but provide a framework for moral action.

8. The Incentive of Pure Practical Reason: Respect for the Law

Agents who act out of respect for the moral law are motivated to act by their recognizing moral considerations as sufficient reasons for action that take priority over and limit the force of the reasons provided by one’s interest in happiness.

Respect for the Moral Law. Respect is the unique feeling that arises from our recognition of the authority of the moral law. It is not a pathological feeling based on inclination but a practical feeling produced by reason itself. Respect is both the proper moral motive and the motivational consequence of recognizing morality's authority.

Humiliation of Self-Conceit. The moral law humiliates our self-conceit by revealing the gap between our actual conduct and the demands of morality. This humiliation is a necessary step in recognizing the sublimity of the moral law and developing respect for it. It is a negative effect that clears the way for a positive moral disposition.

Moral Feeling. Respect for the moral law is the foundation of moral feeling. It is not an independent feeling that grounds morality but a response to the authority of moral principle. This feeling motivates us to act in accordance with duty, even when it conflicts with our inclinations.

9. The Typic of Pure Practical Judgment: Bridging the Sensible and Intelligible

Our concern in moral evaluation, of course, is whether an action instantiates a valid “law of freedom.” Here Kant claims that a law of nature serves as the “type” for a law of freedom.

The Problem of Application. A key challenge in Kant's moral theory is how to apply the abstract moral law to concrete actions in the sensible world. Since the moral law is a law of freedom, it is not directly applicable to events governed by natural laws. This requires a faculty of judgment that can bridge the gap between the intelligible and the sensible.

The Typic of Pure Practical Judgment. Kant introduces the concept of a "typic" to address this problem. The typic is a procedure for judging whether an action is an instance of a universally valid rule of pure practical reason. It involves conceiving of the maxim of the action as a universal law of nature.

Law of Nature as a Type. A law of nature serves as the "type" for a law of freedom, providing a concrete exemplification of the property of lawfulness. By asking whether we could will our maxim to become a universal law of nature, we can assess its moral permissibility. This process allows us to make moral judgments in the sensible world.

10. The Dialectic of Pure Reason: Seeking the Unconditioned

Pure reason always has its dialectic, whether it is considered in its speculative or in its practical use; for it requires the absolute totality of conditions for a given conditioned, and this can be found only in things in themselves.

The Dialectic of Pure Reason. Pure reason, whether speculative or practical, seeks the unconditioned totality of conditions for a given conditioned. This pursuit leads to dialectical illusions, or apparent contradictions, when reason attempts to apply its principles to appearances as if they were things in themselves. The dialectic forces us to critically examine the limits of reason.

The Highest Good as Unconditioned. In the practical sphere, pure reason seeks the unconditioned totality of the object of pure practical reason, which is the highest good. This involves combining virtue and happiness in a necessary connection. However, this combination is not readily apparent in the sensible world.

Resolving the Antinomy. The dialectic of pure practical reason is resolved by recognizing that the connection between virtue and happiness is possible only in a supersensible realm, through the postulates of immortality and the existence of God. This resolution allows us to maintain the validity of the moral law while acknowledging the limitations of our experience.

Last updated: April 1, 2025