 Finally, classification is the key to a theory of technology. The reason is that there exists a systematic connection between complexity and modifiability: the more complex a phenomenon is, the more modifiable it is. The order of nature is a modifiable order. Human action takes place within the limits fixed by nature and consists in replacing the natural order by an artificial one. Comte’s education as an engineer had made him quite aware of the links between science and its applications, which he summarized in an oft-quoted slogan: ‘From science comes prevision, from prevision comes action’. Only death prevented him from writing the System of Positive Industry, or Treatise on the Total Action of Humanity on the Planet, announced as early as 1822.