The concept of a 'system" is an old one: etymologically it derives from the Greek sustēma, from sun- "with" and histanai 'set up," meaning uniting, putting together. But the scientific use of the term is relatively recent; perhaps Carnot was the first to use the term scientifically, when describing the behaviour of steam in his pioneering study of thermodynamics in the 1820s. ¹ In this chapter, in keeping with the growing poststructuralist flavour of the last, and as a bridge from the focus upon Bergson to the focus upon complex systems, I will present a somewhat Foucauldian genealogical interpretation of the concept of 'system", using material from as far back as the early 19th century, but concentrating mainly on the use of the term during the 20th century, and what it has bequeathed to us today. In the next chapter, I will consider Bergson's ideas in conjunction with the contemporary science of "complex systems", or "complexity" as it is often referred to. The current chapter will seek to look at the development of 'systems' thinking prior, and up to, "complex systems."