Will as practical reason is
Definition: The will is the capacity of rational beings to act according to the representation of laws; if reason determines the will infallibly, the being has a good will.
Imperative is
Definition: Representation of an objective principle as necessitating a will that is not perfectly rational. Expressed by an ought.
Hypothetical Imperative is
Definition: Commands an action as a means to achieve some purpose (possible or actual).
Types:
Problematic (possible ends),
Assertoric (happiness).
Categorical Imperative is
Definition: Commands an action as objectively necessary in itself, independent of any end.
“Holds as an apodictically practical principle.”
Maxim is
Definition: A subjective principle of action — the rule the agent actually acts upon.
Opposed to objective law.
Perfect vs. Imperfect Duties
Perfect duty: admits no exception (e.g. not to lie, not to commit suicide).
Imperfect duty: allows latitude (e.g. develop talents, aid others).
Duty is
Definition: Practical necessity of action from respect for law; can only be expressed in categorical imperatives.
Autonomy / Heteronomy
Autonomy: Will gives universal law to itself.
Heteronomy: Will determined by external interests, inclinations, or contingent motives.
Humanity / End-in-Itself
Definition: Every rational being exists as an end in itself, never merely as a means.
Foundation for moral law.
Kingdom of Ends
Definition: A systematic union of rational beings under common self-given universal laws.
Thesis 1 — Only the categorical imperative can ground morality
Argument 1 for Thesis 1
Hypothetical imperatives depend on contingent ends (e.g., “if you want X, do Y”).
Contingent ends cannot ground universal moral necessity.
Argument 2 for Thesis 1
Moral duty requires unconditional, universally binding necessity.
Hypothetical imperatives always allow escape by dropping the end; therefore cannot express moral obligation.
Argument 3 for Thesis 1
Anything empirical (desires, feelings, inclinations) is contingent and cannot ground universality, so morality cannot be based on empirical motives.
Thesis 2 — The supreme moral law is the Universal Law Formula
“Act only according to that maxim which you can will to become a universal law.”
Argument 1 for Thesis 2
A categorical imperative contains no condition; thus the only possible content is conformity of one’s maxim to universal law.
Argument 2 for Thesis 2
When universalized, immoral maxims generate contradictions:
suicide → contradicts nature’s purpose of self-preservation;
lying promise → destroys the practice of promising;
neglect of talents → cannot will universal non-development;
refusal to aid others → cannot will universal lack of help.
Argument 3 for Thesis 2
When we violate duty, we smuggle an exception for ourselves, which reveals we tacitly acknowledge the universal law but break it out of inclination.
Thesis 3 — Rational nature exists as an end in itself
(Humanity = absolute, unconditional worth; must never be used merely as means.)
Argument 1 for Thesis 3
Objects of inclination have only conditional worth; only rational nature has unconditional worth.
Therefore humanity = end in itself.
Argument 2 for Thesis 3
Each rational being necessarily represents their own existence as an end; by universalization, every rational being must be regarded likewise.
Argument 3 for Thesis 3
Misusing others as mere means (lying, coercion, exploitation) violates the very conditions that make moral law possible.
E.g., lying promise: one uses another only as a means.
Thesis 4 — Autonomy is the foundation of morality
(A moral will gives universal law to itself.)
Argument 1 for Thesis 4
If a will is motivated by inclinations or external interests, it becomes heteronomous — its laws are always conditional.
Only a self-legislating will can be unconditionally moral.
Argument 2 for Thesis 4
A lawgiving will cannot depend on interest; otherwise it would need another law above it to restrain self-love.
Therefore autonomy alone grounds categorical imperatives.
Argument 3 for Thesis 4
Duty is the practical necessity of acting from one’s own rational universal law.
If morality came from any external source, duty would collapse into external constraint.
Thesis 5 — The “Kingdom of Ends” is the ideal moral community
Argument 1 for Thesis 5
Universal lawgiving implies mutual legislation: rational beings united under common laws form a kingdom (systematic union).
Argument 2 for Thesis 5
Each person must see themselves as both legislator and subject; this dual role expresses dignity and moral equality.
Argument 3 for Thesis 5
Only rational beings capable of moral law possess dignity, which is above all price.
This grounds the ethical commonwealth.
3 formulation of categorical imperative
1) the Formula of Universal Law, which states that you should only act according to a maxim that you can at the same time will to become a universal law; 2) the Formula of Humanity, which requires you to treat humanity, in your own person or that of another, never simply as a means to an end, but always at the same time as an end; and 3) the Kingdom of Ends, which posits that you must act as if you were a legislating member in a universal kingdom of ends.
