Immanuel Kant
1724–1804, Königsberg, Prussia
German Idealism
The mind does not passively receive the world; it actively shapes it.
“Act only according to that maxim by which you can at the same time will that it should become a universal law.”
The life
Kant was born in Königsberg, then in Prussia, to a saddler's family with a strict Pietist faith. He spent essentially his entire life within a few miles of the city and never saw the sea, though he lectured on geography for decades.
He worked as a private tutor for years and did not become a full professor until he was forty-six. Then came what is called the silent decade: eleven years of publishing almost nothing, ending in 1781 with the Critique of Pure Reason, which he wrote in a few months and which nobody could understand.
He was famously regular, and his afternoon walk is supposed to have been reliable enough to set clocks by, though the story has grown in the telling. Late in life he was formally reprimanded by Friedrich Wilhelm II for his writings on religion and agreed to stay silent on the subject while the king lived.
What shaped the ideas
Kant thought two things were both obviously true and apparently incompatible. Newtonian science described a universe governed by strict causal law, and morality required that people be free enough to be responsible. Hume's scepticism had also shown that empiricism could not even secure causation.
His solution was to distinguish what we can know, the world as it appears under the conditions our minds impose, from things as they are in themselves. Science gets the first with certainty; freedom and morality operate in a space the first cannot reach.
Core arguments
- 01
The Copernican turn
Objects conform to our cognition rather than our cognition to objects.
If knowledge simply copied the world, necessary truths known in advance of experience would be impossible. But we do have them, in mathematics and in the principle that every event has a cause. That is explicable if space, time and the categories are the mind's own contribution to any possible experience.
- 02
Phenomena and noumena
We know things as they appear, never as they are in themselves.
If the mind structures all experience, then everything experienced already carries that structure. There is no way to step outside your own cognitive apparatus to check the unfiltered version. The thing in itself is therefore not unknown in a way further research could fix; it is unknowable in principle.
- 03
The categorical imperative
Act only on maxims you could will to be universal law.
A moral requirement must bind regardless of what you happen to want, so it cannot be based on any particular desire. What remains is the bare form of law: universality. Test a maxim by universalising it. A lying promise fails not because the results would be bad but because universal lying promises would destroy the practice that makes the maxim possible.
- 04
The humanity formula
Treat people always as ends in themselves, never merely as means.
Rational beings set their own ends, which gives them a worth that is not exchangeable for anything: dignity rather than price. Using someone merely as an instrument treats a source of ends as though it were an object, which is a contradiction in how you are actually relating to them.
- 05
Autonomy
Freedom is obeying a law you give yourself.
Being pushed around by desire is not freedom, it is being caused by nature. Nor is obeying an external authority. Genuine freedom is acting on a law your own reason legislates, which is why for Kant morality and freedom turn out to be the same thing viewed from two directions.
Commonly got wrong
- Universalisability is not the golden rule and not a prediction about consequences. The test is whether the maxim could coherently function as a universal law, not whether the results would be pleasant.
- Kant does not say emotions are bad. He says an action has moral worth when done from duty, which is a claim about what makes it praiseworthy, not a recommendation to be cold.
- His lectures on anthropology and geography contain sustained racist claims and a hierarchy of races. These were long treated as separable from the ethics; that assumption is now, rightly, under serious scrutiny.
Works
Critique of Pure Reason 1781, revised 1787
What can be known, and why metaphysics keeps overreaching. Notoriously difficult.
Groundwork of the Metaphysics of Morals 1785
Short, and the standard entry to his ethics. The categorical imperative is here.
Critique of Practical Reason 1788
Freedom, moral law, and the postulates of God and immortality.
Critique of the Power of Judgment 1790
Beauty, the sublime and purposiveness. The foundation of modern aesthetics.
Toward Perpetual Peace 1795
A sketch for international federation that fed directly into the League of Nations and the UN.
Groundwork, section I. It starts from ordinary moral judgements and builds, and it is about thirty pages.
Why they still get taught
Human dignity as a non-negotiable, the language of autonomy in medical ethics, and the structure of modern human rights law all trace to him. Almost every major philosopher since has had to define themselves for or against Kant.
Chapters
- Kant's Categorical Imperative · The Modern Turn
- The Ethics of Artificial Minds · Mind & Modern Ideas
- Beauty Without a Use · The Sense of Beauty
- An Ethics of Care · Naming the Subject