Agreed with Lazzarini. Both Malthus (High Price of Provisions, 1800) and Chalmers (National Resources, 1808) were at least as 'formal' and 'Ricardian' as Ricardo -- Chalmers with considerably more sophistication. For that matter, both Hume's Balance of Trade (1752) and chap X of Malthus's first Essay (1798) may be regarded as coherent and successful attempts to model the dynamic stability of equilibrium. For examples of mathematical modelling in the 18th C -- chiefly by Italians if I remember rightly -- see Theocharis (1961). A. M. C. Waterman