 The stark definition of the human mind and body as distinct, simple substances did not prevent La Forge from describing their union in human nature as a ‘composite subject’ (T 112; THM 39) and as ‘a unity of composition and association’ (T 98; THM 28). It is known from experience that there is some kind of union involved here, which Descartes had struggled to describe in terms of an intermingling of two substances. La Forge describes it more analytically in causal terms; it consists in