Kant’s Philosophy: Reason, Morality, and the Structure of Knowledge
I. Critique of Pure Reason
Kant’s philosophy is based on the coexistence of science and morality. Science operates under determinism (necessity), while morality requires freedom. Humans are subject to both physical laws (necessity) and moral law (freedom). We possess theoretical reason for scientific knowledge and practical reason for moral action.
The Critique of Pure Reason (CPR) explores two main ideas:
- Philosophy as a Science: Can philosophy be a rigorous science?
- Conditions for Science: What are the necessary conditions for scientific knowledge?
To address this, Kant analyzes scientific judgments. There are two types:
- Analytical Judgments: A priori, universal, and necessary (e.g., “All bachelors are unmarried”).
- Synthetic Judgments: Not a priori, contingent (e.g., “The book is red”).
Following Newton, Kant argues that scientific judgments must be a priori (universal and necessary) but also synthetic (informative). Science relies on synthetic a priori judgments.
Kant distinguishes between logic and science, and pure and applied science. We can distinguish two parts:
Formal (Mathematics)
Judgments are a priori but synthetic (e.g., “The shortest distance between two points is a straight line”).
Empirical
Every effect has a cause.
Kant asks: How is a priori knowledge possible? He draws an analogy to the Copernican revolution, suggesting that the subject imposes a priori conditions on experience. Objects must conform to our cognitive structures to be known (idealism). The subject is active in shaping knowledge.
The “thing-in-itself” (noumenon) is unknowable; we only know phenomena (objects as they appear to us). The subject has a priori structures (forms) that determine how we perceive reality.
1. Sensitivity (Transcendental Aesthetic)
1.1 Perception
Knowledge begins with perception. Sensitivity provides us with sensory data (appearances). Appearances can be external (physical) or internal (psychic).
1.2 Space and Time
Universality requires conditions: all external appearances are in space and time; all psychic events occur in time. Space and time are a priori forms of intuition, not concepts.
2. Understanding (Transcendental Analysis)
2.1 Categories
Humans use language to understand and make judgments, relating concepts to perceptions. Knowing something means assigning a predicate to a subject. We need a priori concepts, or categories, to think. Kant identifies 12 categories grouped into four types of judgments:
- Quantity: Universal (Unity), Particular (Plurality), Singular (Totality).
- Quality: Affirmative (Reality), Negative, Limitative.
- Relation: Categorical (Substance/Accident), Hypothetical (Cause/Effect), Disjunctive (Community).
- Modality: Problematic (Possibility/Impossibility), Assertoric (Existence/Non-existence), Apodictic (Necessity/Contingency).
Pure concepts enable judgments. We need:
- Empirical data (experience).
- Space and time (a priori forms).
- Empirical concepts.
- A priori concepts (categories).
2.2 Nature and Reason
Nature conforms to reason. Kant explains causality, opposing Hume. Appearances and categories form phenomena, our understanding of the world. Knowing the categories means knowing the world.
2.3 Scope of Categories
Categories apply only to phenomena, not to things-in-themselves (noumena). We cannot know things like God scientifically.
2.4 Transcendental Idealism
Space, time, and categories are a priori forms of possible experience, not properties of things-in-themselves. We know phenomena, not noumena. Kant defends the reality of a priori forms for phenomena and their ideality concerning noumena.
3. Reason (Transcendental Dialectic)
3.1 Metaphysics and Error
Reason allows us to draw conclusions and chain judgments, seeking higher principles. Metaphysics, unlike science, deals with the unconditioned. Kant identifies errors in traditional metaphysics regarding God, the world, and the self:
- God: False evidence.
- World: Antinomies (contradictions about the world’s finitude).
- Self: Paradoxes.
3.2 Unconditioned and Transcendental Ideas
Humans naturally seek the unconditioned. We have three transcendental ideas (God, world, self) guiding this search. The self is a condition for mental processes but is also conditioned by them (like the eye metaphor). Reason seeks the unconditioned (noumena), studied by philosophy. There are two approaches:
- Dogmatic Metaphysics: The unconditioned exists as a thing-in-itself.
- Kantian Criticism: The unconditioned is a necessary idea of reason, but knowledge of things-in-themselves is impossible. The unconditioned is essential for experience.
II. Morality
Kant’s Critique of Practical Reason explores moral philosophy. It is a formal ethics based on a priori moral norms.
1. Material Ethics
1.1 Supreme Good
Material ethics posits a supreme good (happiness, pleasure) as the ultimate goal.
1.2 Means to an End
Actions are good if they achieve this goal. Knowledge of means is empirical (inductive, contingent), depending on factors like the nervous system. Material ethics sets hypothetical imperatives (if you want X, do Y). These lack binding force if one doesn’t desire the end.
2. Kantian Ethics
Kant advocates for categorical imperatives: unconditional rules not tied to ends (e.g., “Do not steal”). Actions are:
- Conforming to duty:
- Out of duty (categorical).
- Out of interest (hypothetical).
- Contrary to duty.
Moral rules are a priori. We need a universal a priori principle applicable to the empirical world. Maxims (individual rules) should be universalizable into laws. One cannot will something that cannot be willed for all humanity. Only good can be universalized.
2.1 Passions vs. Reason
Actions stem from passions (material, heteronomous, hypothetical) or reason (moral autonomy, categorical, free). The categorical imperative arises from freedom and reason. We can violate it, acting on hypothetical imperatives. Freedom belongs to the noumenal realm. Kant posits an immortal soul and God to ensure moral justice after death, as a necessary postulate of practical reason.