Full Idea
Kant believed in retributive punishment, because he thought that a man would prefer being sent to prison to going to hospital.
Gist of Idea
Retributive punishment is better than being sent to hospital for your crimes
Source
report of Immanuel Kant (Groundwork of the Metaphysic of Morals [1785]) by Isaiah Berlin - The Roots of Romanticism Ch.4
Book Reference
Berlin,Isaiah: 'The Roots of Romanticism' [Pimlico 2000], p.74
A Reaction
That is, even criminals welcome the dignity of being treated as if they are actually responsible for their deeds, and are not just victims of inner forces. Criminals demand free will! Truth is best, though; many of them are not responsible at all.