Full Idea
In all men, as soon as their reason has become ripe for speculation, there has always existed and will always continue to exist some kind of metaphysics.
Gist of Idea
You just can't stop metaphysical speculation, in any mature mind
Source
Immanuel Kant (Critique of Pure Reason [1781], B021)
Book Reference
Kant,Immanuel: 'Critique of Pure Reason', ed/tr. Guyer,P /Wood,A W [CUO 1998], p.147
A Reaction
I love the word 'speculation' in this, because it is the part of metaphysics which always resists logical positivist scepticism about metaphysics. So what if you can't 'verify' it?