is not necessary then it is meaningless. That is the meaning of Occam's Razor." (If everything in the symbolism works as though a sign had meaning, then it has meaning.) 4.04 "In the proposition, there must be exactly as many things distinguishable as there are in the state of affairs, which it represents. They must both possess the same logical (mathematical) multiplicity (cf. Hertz's Mechanics, on Dynamic Models)." 5.47321 "Occam's Razor is, of course, not an arbitrary rule nor one justified by its practical success. It simply says that unnecessary elements in a symbolism mean nothing. Signs which serve one purpose are logically equivalent; signs which serve no purpose are logically meaningless." and on the related concept of "simplicity": 6.363 "The procedure of induction consists in accepting as true the simplest law that can be reconciled with our experiences." Uses Science and the scientific method In science, Occam's razor is used as a heuristic to guide scientists in developing theoretical models rather than as an arbiter between published models. In physics, parsimony was an important heuristic in Albert Einstein's formulation of special relativity, in the development and application of the principle of least action by Pierre Louis Maupertuis and Leonhard Euler, and in the development of quantum mechanics by Max Planck, Werner Heisenberg and Louis de Broglie. In chemistry, Occam's razor is often an important heuristic when developing a model of a reaction mechanism. Although it is useful as a heuristic in developing models of reaction mechanisms, it has been shown to fail as a criterion for selecting among some selected published models. In this context, Einstein himself expressed caution when he formulated Einstein's Constraint: "It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience." An often-quoted version of this constraint (which cannot be verified as posited by Einstein himself) reduces this to "Everything should be kept as simple as possible, but not simpler." In the scientific method, parsimony is an epistemological, metaphysical or heuristic preference, not an irrefutable principle of logic or a scientific result. As a logical principle, Occam's razor would demand that scientists accept the simplest possible theoretical explanation for existing data. However, science has shown repeatedly that future data often support more complex theories than do existing