Moore's blunt proof that the external world exists

Facing radical sceptics who doubted an external world could ever be proven, G. E. Moore raised one hand, said 'here is one hand,' raised the other, and declared he'd just proven at least two external objects exist. He argued this common-sense proof was more certain than any clever argument for doubting it.

— G. E. Moore, Proof of an External World — Proceedings of the British Academy, 1939