Curie's Principle

physical sciences. Reasoning based on notions of symmetry has been evident in science since antiquity1 but the arguments employed are usually vague or implicit.2 Even if the sole function of the principle is to render such reasoning more precise and explicit an exposition of it is desirable in so far as it clarifies the status of and the assumptions involved in the arguments. One explanation of the lack of reference to the principle would be that it is implied by some other principle in common use. We are led to ask, then, if Curie's principle can be derived from some more general assertions. We shall show that the principle can be derived from the invariance properties of physical laws but that this fact by no means renders the principle redundant. Our remarks so far have been based on the assumptions that the principle is valid and can be formulated with sufficient precision for it to be of use in the physical sciences. If either of these assumptions were to prove false then we would, of course, have a very definite answer to our puzzle over the lack of attention paid to the principle. Freudenthal (I968, p. 420) has suggested that the principle acquires its generality by being necessarily vague. In this respect he attributes to Curie's principle a status similar to that of Leibniz's principle of sufficient reason.3 That such a claim is