It is strange to note so little discussion of the exclusion principle in the philosophical literature. Philosophers, largely engrossed in their perennial problems, are hardly aware of the fact that, during the last two decades, there has been introduced into physical methodology a principle of utmost philosophical importance, easily rivaling that of relativity and, in some respects, indeed that of causality. Discovered by Pauli in 1925, it immediately elucidated a whole realm of physical facts and was accepted by physicists with (...) wide acclaim. Called the exclusion principle—or Pauli principle, or principle of anti-symmetry—it was embodied in the axiomatics of quantum mechanics; its peculiar methodological significance passed out of view. (shrink)

Although there is a complete consensus among working physicists with respect to the practical and operational meanings of quantum states, and also a rather loosely formulated general philosophic view called the Copenhagen interpretation, a great deal of confusion and divergence of opinions exist as to the details of the measurement process and its effects upon quantum states. This paper reviews the current expositions of the measurement problem, limiting itself for lack of space primarily to the writings of physicists; it calls (...) attention to inconsistencies and proposes resolutions. Except for a summary of the properties of statistical matrices which are needed in Part II, the first part is non-mathematical and deals largely with two kinds of probability, reducible and irreducible probabilities, which need to be distinguished for a proper understanding of the measurement act. (shrink)

The trouble with the idea of measurement is its seeming clarity, its obviousness, its implicit claim to finality in any inquisotory discourse. Its status in philosophy of science is taken to be utterly primitive; hence the difficulties it embodies, if any, tend to escape detection and scrutiny. Yet it cannot be primitive in the sense of being exempt from analysis; for if it were every measurement would require to be simply accepted as a protocol of truth, and one should never (...) ask which of two conflicting measurements is correct, or preferable. Such questions are continually being asked, and their propriety in science indicates that even measurement, with its implication of simplicity and adroitness, points beyond itself to other matters of importance on which it relies for validation. (shrink)

Recent discussions in the physical literature, designed to clarify the logical position of modern physical theory, have brought to light an amazing divergence of fundamental attitudes which may well bewilder the careful student of physics as well as philosophy. Quantum mechanics, representing an abstract formalism, should be capable of having its logical structure analyzed with great precision like any other mathematical discipline. Its consequences in all problems to which its method can be applied are so unambiguous, consistent, and successful in (...) predicting physical experience as to disperse immediately all thoughts of possible discrepancies in its fundamental texture. Yet it must be said that even the founders of quantum theory are not in harmony in their various expositions of the bases of that theory. However, while this situation seems disquieting on the face of it, there is no cause for serious brow raising, for it is a fact that there exists agreement with regard to the central axioms of the theory, and that the ambiguities affect only their philosophical interpretation, a field in which differences of opinion may at present be honestly entertained. (shrink)

This is the second, mathematically more detailed part of a paper consisting of two articles, the first having appeared in the immediately preceding issue of this Journal. It shows that a measurement converts a pure case into a mixture with reducible probabilities. The measurement as such permits no inference whatever as to the state of the physical system subjected to measurement after the measurement has been performed. But because the probabilities after the act are classical and therefore reducible, it is (...) often possible to adjust them so that Von Neumann's projection postulate is true. Among the more specific features dealt with in Part II is the occurrence of negative joint probabilities for the measurement of non-commuting operators in certain (not all!) quantum states. The general conclusions reached are stated at the end of the article. (shrink)

In a recent paper, Prugovečki offered a theory of simultaneous measurements based upon an axiomatic description of the measurement act which excludes certain illustrations of simultaneous measurement previously discussed by the present writers. In this article, the fundamental conceptions of state preparation, state determination, and measurement which underlie our research are compared to Prugovečki's interpretations of the analogous constructs in his theory of measurement.

Methodology might be understood to mean a description of various individual procedures which have led to the successful solution of specific problems. In studying the subject of physics from this point of view, i.e. with special emphasis on method, one would naturally turn his attention to the traditional divisions of experimental and theoretical physics, the former with its measuring devices and the latter with its mathematical technique. In no other sense than this does the term methodology make any direct appeal (...) to the working physicist, and if you would ask him to define his methods he would probably answer with a description of experimental technique or the methods of setting up and solving differential equations. His answer would tell you how he solves his problems, but hardly how he finds them and why he solves them. (shrink)

Do masses, electrons, atoms, magnetic field strengths, etc., exist? Nothing is more surprising indeed than the fact that in these days of minute quantitative analysis, of relativistic thought, most of us still expect an answer to this question in terms of yes or no. The physicist frowns upon questions of the sort: is this object green?; or what time is it on a distant star? For he knows that there are many different shades of green, and that the time depends (...) on the state of motion of the star. Almost every term that has come under scientific scrutiny has lost its initially absolute significance and acquired a range of meaning of which even the boundaries are often variable. Apparently the word to be has escaped this process. (shrink)

The philosophy of quantum mechanics has often been conceived by physicists as a collection of dogmas concerning what can be measured, observed and known. To this branch of dialectics the present paper does not attempt to contribute, chiefly because it is written from the conviction that no part of science, nor any philosophy, can safely predict what may be feasible or knowable. Rather, this brief essay endeavors to expose the epistemology of quantum physics in a way which allows it to (...) be recognized as an extension of the ordinary processes of cognition, as the continuation of a line which starts in sensory perception, leads straight through the methods of classical physics into quantum mechanics and shows no signs of terminating even there. (shrink)

The nature of time is one of the crucial problems in the philosophy of science and it cannot be solved by an appraisal of past formulations of the time concept, nor by introspective examination of our awareness of time. Among the philosopher's tasks is the seemingly thankless one of scrutinizing the advance of modern science for significant facts and ideas, and to integrate these into the larger notions he has formed of time. Recent physics bears suggestions of peculiar interest in (...) this regard; chief among them is the theory of quantum electrodynamics developed by Feynman which involves reversals in the course of time and thereby cherishes, in the minds of many, an age-old phantasy of more than scientific appeal. To appraise that theory in philosophic terms is the purpose of this note. (shrink)

This paper is the forerunner of an extensive logical analysis of the relativity idea, in which an axiomatic structure based upon the principles of topology is developed. It is meant to expose the manner in which relativity stretches from the pole of pure conception to that of factual observation, from the a priori to the a posteriori. We take pains to show, in connection with special relativity, precisely which elements are postulational and which are verifiable empirically. Our attempt can be (...) somewhat naively characterized as an effort to show how misguided it is to "derive" relativity from such experimental facts as the Michelson-Morley experiment--as so many textbooks profess to do. (shrink)

Stranger and more momentous than the strangest of scientific theories is the appearance of God on the intellectual horizon of contemporary science. From Einstein, Planck, and Heisenberg, to Margenau, Hawking, and Eccles, some of the most penetrating modern minds have needed God in order to make sense of the cosmos.

First Published in 1972. Routledge is an imprint of Taylor & Francis, an informa company.

The disagreement with regard to the validity of the principle of causality, existing to-day among scientists, has its roots in the diversity of definitions of the principle itself rather than in a problematic scientific situation. As far as the formulation of quantum theory is complete its bearing upon philosophical questions can be fixed with precision provided the questions are phrased intelligibly. But a question is intelligible from a scientific point of view only if it satisfies two conditions: the meaning of (...) its terms must be fixed; it must be in accord with the conventions of the science to which the question is put. (shrink)

In theories of the mobilities of ions in gases a rather precise knowledge is required of the forces which are called into play when an ion approaches a neutral molecule; for it is by virtue of these forces that ions are deflected from their paths and that their drift along the electric force is impeded. Again, the current question whether ions, in their motion through a gas, form “clusters”, that is, whether they surround themselves by one or even more layers (...) of neutral molecules, can be decided theoretically only on the basis of a rather precise knowledge of the interactions. (shrink)

The present paper is concerned chiefly with the problem of scientific prediction. It aims at a factual analysis of the processes leading to prediction, and ventures an appraisal, in the light of this analysis, of some modern and unconventional theories of probability and truth. But although prediction is here chosen as the central issue of discussion, I do not wish to imply that, in its usual sense, it is the only or even the dominant issue of scientific research.

The science of the 19th and early 20th century permitted the view that all human experience is subject to the deterministic laws of physics. Reality was conformable with these laws, and the laws could be used to designate what is real.