Full Idea
The grounds upon which 'this' world has been designated as apparent establish rather its reality - another kind of reality is absolutely undemonstrable.
Gist of Idea
The grounds for an assertion that the world is only apparent actually establish its reality
Source
Friedrich Nietzsche (Twilight of the Idols [1889], 2.6)
Book Reference
Nietzsche,Friedrich: 'Twilight of the Idols and The Anti-Christ', ed/tr. Hollingdale,R.J. [Penguin 1972], p.39