Life and inertia or matter are two antagonistic principles or tendencies. Life is the positive and active principle; reality and duration are predicable only of life. Matter is an “inversion” or “interruption” of life; its value is negative to life and to reality. “All that which seems _positive_ to the physicist and to the geometrician would become, from this new point of view, an interruption or inversion of true positivity, which would have to be defined in psychological terms.”[120] Matter is a determination of reality in much the same sense as that in which the reality of the Platonic idea suffers diminution under the influence of the principle of not-being, resulting in a world of sensible experience or of appearance. Bergson points out that the real in Plato is the timeless, motionless, definite idea, and the relatively unreal is the ever-changing “infinite” or indefinable datum of experience, to which duration is essential. Bergson reverses the Platonic metaphysics: reality is the ever-changing and indefinable; rather, it is change itself. “There are no things, there are only actions.” “... things and states are only views, taken by our mind, of becoming.”[121] The principle antagonistic to reality gives rise to the timeless, definite concept, which is a view or appearance of reality operated by intelligence in the service of action. As our practical interests break up the continuum of time into discrete states, so they break up the continuum of matter into distinct bodies. The active antagonism of time, which is pure quality or heterogeneity, and space, which is pure quantity or homogeneity, results in the world of our experience, comprising “states” of consciousness and things or objects. The relation between life and matter in the evolution of the world, Bergson represents by the figure of a generation of steam in a boiler.[122] Life, the positive principle, streams or flows, like the steam, by the force which is its very nature. In its course, this vital impetus is checked, as a jet of steam is checked, by its condensation, and falls back upon itself in drops, retarding, but not annihilating, the flow. But we are warned that the figure must be corrected in that the interruption or inversion of the impetus is due to a principle inherent in the impetus itself, not to an external determination. If there were such an external principle, the two would seem coördinate in reality, but the reality of matter is as the reality of _rest_, which, as the negation of motion, is nothing positive, yet is not a mere naught.