Walk through a giant thinking machine, find no thought inside

Leibniz asks you to imagine a machine that could think and feel, enlarged to the size of a mill so you could walk through its gears. Inside, he says, you'd see only parts pushing on parts, never anything resembling a perception. He concluded consciousness can't be explained by mechanism alone.

— Gottfried Wilhelm Leibniz, Monadology — Section 17, 1714