In the contemporary systems view man is not a sui generis phenomenon that can be studied without regard to other things. He is a natural entity, and an inhabitant of several interrelated worlds. By origin he is a biological organism. By work and play he is a social role carrier. And by conscious personality he is a Janus-faced link integrating and coordinating the biological and the social worlds. Man is, in the final analysis, a coordinating interface system in the multilevel hierarchy of nature.

p. 79. - Introduction to Systems Philosophy (1972)