This chapter will briefly introduce the principles of General Systems Thinking (GST) as defined by classic literature on the subject (Ackoff, 1971; Battista, 1977; Bertalanffy, 1968; Boulding, 1956; Churchman, 1968; Waelchi, 1992; Weinburg, 1975). In particular, this chapter will contrast two opposing operational research (OR) views about systems thinking; the ‘reductionistic’ (‘hard’) approach...