Free association, known as the Fundamental Rule, is the cornerstone of psycho-analytic technique and research. Yet there has been little systematic consideration of it.

The historical roots of the concept go back to Aristotle, and particularly to the English school of sensualism and associationism, with Hobbes, Locke, Hume, James and John Stuart Mill, Hartley, Bain, Spencer, Brentano, Galton, Herbart, Lipps, on to Wundt and Freud, and then to nearly all of modern psychology.