Another idea fails when applied to itself

[lulie]

There's an idea that goes: the only thing which exists is the material universe and the matter within it, which interacts according to the laws of physics. I think it's called mechanism; let's go with that. Anyway, mechanism is just an idea, not a physical fact. So according to itself, it doesn't exist.

Update: The word I was looking for is 'materialism'. I used 'mechanism' due to misunderstanding of this.