Foundations Of Cognitive Science

Mental Chemistry

John Stuart Mill modified his father’s theory of associationism (Mill & Mill, 1869; Mill, 1848) in many ways, including proposing a mental chemistry “in which it is proper to say that the simple ideas generate, rather than they compose, the complex ones” (Mill, 1848, p. 533).  Mill’s mental chemistry is an early example of emergence, where the properties of a whole (i.e. a complex idea) are more than the sum of the properties of the parts (i.e. a set of associated simple ideas).  “The generation of one class of mental phenomena from another, whenever it can be made out, is a highly interesting fact in mental chemistry; but it no more supersedes the necessity of an experimental study of the generated phenomenon than a knowledge of the properties of oxygen and sulphur enables us to deduce those of sulphuric acid without specific observation and experiment” (Mill, 1848, p. 534).


  1. Mill, J., & Mill, J. S. (1869). Analysis Of The Phenomena Of The Human Mind (A new edition, with notes illustrative and critical / by Alexander Bain, Andrew Findlater, and George Grote. ed.). London: Longmans, Green, Reader.
  2. Mill, J. S. (1848). A System of Logic, Ratiocinative and Inductive; being a connected view of the principles of evidence and the methods of scientific investigation. New-York,: Harper & Brothers.

(Added October 2010)