This time once again it has been my chief aim to make no sacrifice to an appearance of being simple, complete or rounded off, not to disguise problems and not to deny the existence of gaps and uncertainties. In no other scientific field would it be necessary to boast of such modest intentions. They are universally regarded as self-evident; the public expects nothing else. No reader of an account of astronomy will feel disappointed and contemptuous of the science if he is shown the frontiers at which our knowledge of the universe melts into haziness. Only in psychology is it otherwise. There mankind's constitutional unfitness for scientific research comes fully into the open. What people seem to demand of psychology is not progress in knowledge, but satisfactions of some other sort; every unsolved problem, every admitted uncertainty is made into a reproach against it. Whoever cares for the science of mental life must accept these injustices along with it.