In a general way it may be said that to think in terms of systems seems the most appropriate conceptual response so far available when the phenomena under study—at any level and in any domain—display the character of being organized, and when understanding the nature of the interdependencies constitutes the research task. In the behavioral sciences, the first steps in building a systems theory were taken in connection with the analysis of internal processes in organisms, or organizations, when the parts had to be related to the whole.

p. 21. - The Causal Texture of Organizational Environments (1963)