Our understanding of complexity can be seen as a piecemeal accumulation over time; but seen over the long perspective of the history of thought, it can also be arranged in a series of “major transitions.” In this chapter, we propose six major transitions in understanding, each relating to recognition of a new perspective within which to view urban complexity: that of living beings as complex things; of Homo sapiens as just another species; of “organised complexity" as a “good” thing; of the necessary social dimension of urban complexity; of diversity as a necessary dimension of social complexity, and finally the “wicked” nature of intervention in complexity. These historical transitions paved the way for complexity sciences to be incorporated into theories of cities from the 1990s.
