Full Idea
What has first to have itself proved is of little value.
Gist of Idea
Anything which must first be proved is of little value
Source
Friedrich Nietzsche (Twilight of the Idols [1889], 1.05)
Book Reference
Nietzsche,Friedrich: 'Twilight of the Idols and The Anti-Christ', ed/tr. Hollingdale,R.J. [Penguin 1972], p.31