When the psycho-analyst writes to a patient, ‘The submerged instincts of the cave-man are doubtless prompting you to gratify a violent impulse,’ he does not refer to the impulse to paint in water-colours; or to make conscientious studies of how cattle swing their heads when they graze. Yet we do know for a fact that the cave-man did these mild and innocent things; and we have not the most minute speck of evidence that he did any of the violent and ferocious things.
