General systems theory (in the narrow sense of the term) is a discipline concerned with the general properties and laws of systems. A system is defined as a complex of components in interaction, or by some similar proposition. Systems theory tries to develop those principles that apply to systems in general, irrespective of the nature of the system, of their components, and of the relations or forces between them. The system components need not even be material, as, for example, in the system analysis of a commercial enterprise where components such as buildings, machines, personnel, money and good will of customers enter.

p. 69 - Robots, Men and Minds' (1967)