Königsberg, 1724–1804

Immanuel Kant

Every event in nature has a cause, our actions included. Yet the moral law tells us what we ought to do, and "ought" implies "can". So we must be free, in a sense no science could ever find, and the compatibilist's freedom is a wretched subterfuge.

The view

In the Critique of Pure Reason (1781), Kant argued that causation is one of the forms through which the mind orders experience. Every event we could ever observe must therefore have a cause, according to a rule. That includes human actions, considered as events in the world. If you knew a person's character and circumstances well enough, Kant said, you could predict their conduct as surely as an eclipse.

But the world as we experience it, the world of appearances, is not the whole story. Behind it lies the world of things as they are in themselves, of which we can know nothing. And there, causation does not apply. That leaves room, though no more than room, for a freedom that is not a link in any natural chain: the power to begin a series of events from oneself. Kant called it transcendental freedom.

The argument

If freedom is only the working of inner causes, then it is no better than the freedom of a turnspit, which, once wound up, also carries out its movements by itself. Kant, Critique of Practical Reason (1788), our paraphrase

In the Groundwork (1785) and the second Critique (1788), Kant argued that we cannot help acting "under the idea of freedom". When you deliberate, you cannot regard your conclusion as fixed in advance by causes; you have to treat yourself as the author of your choice, answerable to reasons. Above all, morality commands you to do your duty whatever your inclinations, and an "ought" makes sense only if you can obey it. The moral law is the evidence of our freedom, and freedom is the condition of the moral law. See an action from the two standpoints.

It was in this setting that Kant dismissed the compatibilism of his predecessors as a "wretched subterfuge". They had answered the problem of free will by redefining freedom as action from internal causes. But an internal cause is still a cause in the natural chain. A turnspit, the clockwork device that turned meat over a fire, also moves by its own internal mechanism once it is wound. If that counted as freedom, the turnspit would be free.

Where he meets Dennett

More than either would expect. Kant insisted that from the standpoint of science, human actions are fully caused and predictable; he was no Epicurean. And his claim that a deliberating agent must regard itself as free is close to Dennett's: deliberation needs an open future from the agent's point of view, however determined it is from outside. Dennett's intentional stance, which treats a system as a rational agent because that is the only useful way to understand it, is a naturalised cousin of the practical standpoint.

Where they part

On the turnspit, directly. Dennett's reply is that the difference between a person and a turnspit is enormous, and it is a difference in design. A turnspit cannot notice that the meat is burning, learn, deliberate or be persuaded; a person can. Kant thought no difference of mechanism could ever add up to freedom; Dennett thought the right mechanisms are all freedom ever was. And Dennett had no use for things in themselves, a realm beyond all possible evidence where freedom hides. For him, a freedom that makes no difference anywhere in nature is not worth wanting.

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Further reading

• Immanuel Kant, Groundwork of the Metaphysics of Morals (1785), section III; translated by Mary Gregor and Jens Timmermann (Cambridge, 2012).
• Henry E. Allison, Kant's Theory of Freedom (Cambridge, 1990).
• Kant's moral philosophy, Stanford Encyclopedia of Philosophy.