DESCARTES (René). Principia philosophiæ. Amsterdam, Louis Elzevier, 1650 - Specimina philosophiæ. Ibid, 1650 - Passiones animæ. Ibid. 1650. 3 works in one volume in-4, grained calf, spine decorated, edges mottled (Binding of the period). Second collective edition of Descartes' philosophical works, the three parts of which were sold separately or brought together under a general title. This is the second edition of the Principia and the Specimina (the Latin translation of the Discourse of Method, the Dioptric and the Meteors), after the original of 1644, as well as the Latin translation of the Passions of the Soul, a treatise published in French in 1649. Numerous woodcut figures and diagrams in the text. Covers and corners worn, first few leaves slightly gnawed in the margins. Willems, n°1106 - Guibert, 121/4, 105/2, 158/8.