The concept of energy, the premier concept of physics and indeed of all science, is here investigated from the standpoint of its early historical origin and the philosophical implications thereof. The fundamental assumption is made that the root of the concept is the notion of invariance or constancy in the midst of change. Salient points in the development of this idea are presented from ancient times up to the publication of Lagrange'sMécanique Analytique (1788).

It is the aim of this paper to examine certain aspects of a point of view which has attracted much attention in physical methodology. This is the standpoint known as operationalism. We wish to discuss its significance in the construction and interpretation of physical theories.The essential meaning of operationalism in physics is that physical concepts should be defined in terms of actual physical operations. On this view there is no meaning to a concept unless it represents an operation which can (...) be performed in the laboratory. Thus the term “pressure of a gas” signifies nothing until an operation is described which constitutes the measurement of pressure. When one thinks of pressure one must think. of some actual apparatus, such as, for example, some glass and rubber tubing and some mercury and certain operations performed using these until finally one gets a pointer reading which one calls the pressure of the gas. The same stand is taken with respect to length, time, velocity, acceleration, temperature, etc. (shrink)

In the fourteenth century William of Occam in the course of his attack on the medieval scholastic philosophy enunciated his famous “razor”: Entia non sunt multiplicanda praeter necessitatem. This is the classic claim for the description of nature in terms of the minimum possible number of fundamental concepts. It was presumably so recognized by Newton in the third book of his “Principia” in 1687 when he wrote: “We are to admit no more causes of natural things than such as are (...) both true and sufficient to explain their appearances. To this purpose the philosophers say that Nature does nothing in vain, and more is in vain when less will serve; for Nature is pleased with simplicity and affects not the pomp of superfluous causes.”. (shrink)

The modern theoretical physicist is a strange creature. Perhaps in every age the theoretical physicist has seemed so to his contemporaries who took the trouble to observe and think about him. There seems, for example, something almost too magical in the uncanny way in which he pulls a brand new atomic particle out of a theory, a way that reminds us of a rabbit being produced out of a hat. This is usually done in an off-hand manner with a considerable (...) amount of patter of a highly abstract symbolic character but with a few words inserted in the right places for the benefit of the experimental physicist and a final prediction that if the experimenter does thus and so in the laboratory he will find a certain result. No wonder the observer marvels when the answer comes out right. But as he thinks further he is inclined to wonder whether it is necessary or desirable for the details of the process which led to the result to be so unintelligible. For unintelligible they seem to be to a great many people who are directly concerned with their understanding, to the people who for years have been laboring under the belief that they are engaged in the task of finding out how Nature works. What is this curious process whose whole task, according to one distinguished exponent of it, is merely to predict experimental results, and what is its future likely to be? These are the questions we are setting for ourselves in the present discussion. It is unlikely that the answers given here will satisfy everybody, but it is reasonably certain that nobody who aspires to an interest in science can fail to attach some meaning to them whether or not he agrees. (shrink)