Full Idea
Kant's four illustrations of the Categorical Imperative are: the contradiction of suicide, the contradiction of false promises, the contradiction of neglecting your talents, and the contradiction of neglecting charity.
Gist of Idea
Suicide, false promises, neglected talent, and lack of charity all involve contradictions of principle
Source
report of Immanuel Kant (Groundwork of the Metaphysic of Morals [1785], 422.53) by PG - Db (ideas)
Book Reference
Kant,Immanuel: 'The Moral Law (Groundwork of Morals)', ed/tr. Paton,H.J. [Hutchinson 1948], p.85