Showing the contribution of its predecessors, as basic element for the elaboration of these slight knowledge. They had been created having finally, to solve the problem of devir, that it are initiated for the jnicos and that they had gained greater repercussion with the theoretical shock between Heraclitus whom devir admitted as essence of the things and Parmnides that defended the being, that is, the immutability as essence of the beings. As solution the estagirita presents the slight knowledge of act and power admitting at the same time devir and the permanence as inherent elements to the beings. When displaying its notion it establishes relations of value, causalidade and composition between the act and power. its relations with the substance. Word-Key: Act. Power.

Devir. Introduction One of the subjects most intriguing of the old philosophy was on question of devir, that is, of the change. Without a doubt, the great solucionador of this problematic rejection Aristotle who with the creation of the slight knowledge of act and power, explained in consistent way the question of the changeability them things, however, the contribution of its predecessors, the jnios must be recognized, the Heraclituses, Parmnides, Anaxgoras and Plato, that by means of its reflections had contributed so that Aristotle created the concept of act and power. For the development of this study the bibliographical research was used as methodology, having as theoreticians JOLIVET (1972), BURNET (2007), MONDIN (2006) and REALE (2001). Under most conditions Scott Mead would agree. The predecessors of Aristotle the first philosophers, known as daily pay-socrticos, had centered its reflections on the thematic one of cosmo, in the attempt to understand the principle collator and the supreme cause, physis, of all the things.