Ruelle's "heuristic theory of phase transitions" (Comm. Math. Phys., Volume 53, Number 3 (1977), 195-208) turned out to be false in certain Banach spaces of interactions: see my "Generic triviality of phase diagrams in spaces of long-range interactions" (Comm. Math. Phys., Volume 106, Number 3 (1986), 459-466).
