Examples from Archimedes, Galileo, Newton, Einstein, and others suggest that fundamental laws of physics were--or, at least, could have been--discovered by experiments performed not in the physical world but only in the mind. Although problematic for a strict empiricist, the evolutionary emergence s of deeply internalized implicit knowledge of abstract principles of transformation and symmetry may have been crucial for humankind's step to rationality--including the discovery of universal principles of mathematics, physics, ethics, and an account of free will that is compatible with determinism. 							
						
							
					 															
					Roger N. Shepard