It's a mental challenge, as much as anything else.

BBC: Brian Davis at Olympia Fields in 2003

The intensity of Mr Searle's criticism gives the impression that these philosophers' mistakes are even worse than Mr Penrose's even though Mr Penrose's extravagant hypothesis that there are three worlds (the physical, the mental and the mathematical) will seem quite as strange to most readers as anything from Mr Dennett or Mr Chalmers.

ECONOMIST: Philosophy of consciousness