Immanuel Kant 1724-1804

Rationalist until age of 50, then read

Hume, who, in his own words,

“awakened me from my dogmatic slumbers”

Then wrote

Critique of Pure Reason

Kant Background

Famous Epigram:

Man is the lawgiver of nature

Philosophical “Copernican Revolution”:

Assume knowledge or morality is real, then examine presuppositions that make it possible

Famous Distinction:

Phenomenal vs. Noumenal

Kantian Moral Theory

Groundwork of the

Metaphysics of Morals

Assumes morality is possible. So free-will presupposed: we can be


Argument then is to find the basis by which we can rule ourselves: apodictic a priori synthetic truth: the concept of law itself:

The Categorical Imperative

Distinctions 1-3

1. person / thing

2. action / passion

3. moral-immoral / amoral

Persons and actions are characterized by the top term in each case, animals and behavior by the bottom term

Not all human beings are persons, nor viceversa.

Behavior ≠ Action.

Action is caused by agent, behavior is not.

Distinctions 4 & 5

4. reason / inclination

5. autonomy / heteronymy

Kant understands reason to influence action via the will.

Autonomy is freedom: not freedom

from natural law, but freedom to make laws for oneself.

Autonomy is necessary for morality.

Distinctions 6 & 7

6. duty / desire

7. categorical imperative / hypothetical imperative

Morality requires autonomy, self-rule by reason, which requires categorical imperative.

Rough form of argument

But what can reason command without any inclination?

[Hume: “Reason is and ought to be the slave of the passions.”]

All that is left is the form of law itself.

SO: There is but one categorical imperative:

“…act only in accordance with that maxim through which you can at the same time will that it become a universal law.”]


Act only in accordance with that maxim through which you can at the same time will that it become a universal law.

[actually 2 or 3 other formulations]

Maxim: the principle on which one acts; the command given oneself by the will. Maxims are hypothetical imperatives.



Two sorts of failures of maxims

(re: universalizability):

Impossibility of maxim becoming universal law: lying, theft, …

- Perfect duties

Impossibility of willing maxim to become universal law

- Imperfect duties