The separation of psychology from the basic assumptions of biology is purely artificial, because the human psyche lives in indissoluble union with the body.
And since these biological assumptions hold good not only for man but for the whole world of living things, the scientific foundation on which they rest obtains a validity far exceeding that of a psychological judgment, which is valid only in the realm of consciousness.
It is therefore no matter for surprise if the psychologist is often inclined to fall back on the security of the biological standpoint and to borrow freely from physiology and the theory of instinct.
Nor is it astonishing to find a widely accepted point of view which regards psychology as merely a chapter in physiology.
Although psychology rightly claims autonomy in its own special field of research, it must recognize a far-reaching correspondence
between its facts and the data of biology. ~Carl Jung, CW 8, Para 232