The crucial question which confronts us in psychology and other aspects of the science of man is precisely this chasm between what is abstractly true and what is existentially real for the given living person. Rollo May
Natural science will in time incorporate into itself the science of man, just as the science of man will incorporate into itself natural science: there will be one science. Karl Marx
Hitherto, the science of Man has been limited to researches... respecting some of its laws, to results deduced from single or insulated observations, and to theories often based on mere glimpses; and these constitute pretty nearly all the materials it possesses. Adolphe Quetelet