Biologists and psychologists often have resorted to rather amusing gestures and have deliberately ignored possible lines of inquiry in order to imitate as closely as possible the physicists and the astronomers. Just as matter was thought to consist of combinations of atoms, so living organisms consisted of cells, and complex acts of behavior were seen to consist of combinations of simple reflexes. The cell and the reflex, being the irreducible minimum of physiology and of psychology, were said to be the realities which constituted the nature of the organism and its acts. All phenomena of life were but combinations of these elemental realities. Find the smallest particles in the combination, show how by a mechanical principle they are inevitably placed in certain temporal and spacial and other quantitative relationships, and behold, science has led you to _Reality_. All this seemed to be very certain in the nineteenth century; it alone was _knowledge_, all else was mere opinion and error. Professor Whitehead says, “But the progress of biology and psychology has probably been checked by the uncritical assumption of half-truths. If science is not to degenerate into a medley of _ad hoc_ hypotheses, it must become philosophical and must enter upon a thorough criticism of its own foundations.... “There persists, however, throughout the whole period the fixed scientific cosmology which presupposes the ultimate fact of an irreducible brute matter, or material, spread throughout space in a flux of configurations. In itself such a material is senseless, valueless, purposeless. It just does what it does do, following a fixed routine imposed by external relations which do not spring from the nature of its being. It is this assumption that I call ‘scientific materialism.’” “The progress of science has now reached a turning point. The stable foundations of physics have broken up: also for the first time physiology is asserting itself as an effective body of knowledge, as distinct from a scrap-heap. The old foundations of scientific thought are becoming unintelligible. Time, space, matter, material, ether, electricity, mechanism, organism, configuration, structure, pattern, function, all require reinterpretation. What is the sense of talking about a mechanical explanation when you do not know what you mean by mechanics?”