Full Idea
Rational nature exists as an end in itself; this is the way in which a man necessarily conceives his own existence.
Gist of Idea
Rational beings necessarily conceive their own existence as an end in itself
Source
Immanuel Kant (Groundwork of the Metaphysic of Morals [1785], 429.66)
Book Reference
Kant,Immanuel: 'The Moral Law (Groundwork of Morals)', ed/tr. Paton,H.J. [Hutchinson 1948], p.91