A great many philosophers have thought it impossible that there should exist two distinct theories between which no possible evidence could discriminate. This doctrine, and more rarely its denial, have often been the cynosure of dogmas and disputes about conventions within physical theory, about simplicity, about measurement in quantum mechanics, and most recently, about radical translation. The list is long enough to make it important to know whether or not the doctrine is true. I shall argue that it is, indeed, not true.

The thesis that empirically equivalent theories are synonymous was central to Hans Reichenbach's philosophy of science, and especially to his notion of ‘equivalent descriptions’ and to his account of simplicity:

The logical analysis of the structure of scientific theory is a task which is central to any comprehensive philosophy of science, and in this sphere no philosopher has contributed more incisively than Rudolf Carnap. The clarity and rigor of his analyses have always made them apt candidates for fruitful discussion and criticism, and Professor Carnap's last proposal dealing with the problem of theoretical analyticity is, I hope to show, no exception to this rule. For my aim here is to take advantage of the rigor of Carnap's formulation by developing its consequences in some detail. The results which emerge from such a development are then employed to overcome some of the more weighty objections against the possibility of drawing an analytic-synthetic distinction for theoretical systems.

It is customary to draw a distinction between statements unconfirmable in practice and statements unconfirmable in principle. It may be impossible, for example, to confirm the statement “The star most distant from us in the universe has recently doubled in size,” but this impossibility is not of a logical kind. We could conceive of tests which would either confirm or disconfirm the statement, even if in fact we cannot carry them out. In contrast, the statement ‘Everything has recently doubled in size’ cannot be confirmed for logical reasons, or so some philosophers have claimed. If everything were to double in size, including the very measuring rods used to detect expansions, it would be logically impossible, so the argument runs, to either confirm or disconfirm the above statement.

In the development of the theory of subjective probability and in discussions about it an important role has been played by de Finetti's representation theorem and by a number of related results presented in de Finetti's classic monograph. This theorem, together with the notion of exchangeability (among its aliases there are the terms equivalence, permutability, and symmetry), was originally put forward by Bruno de Finetti as a solution to a problem to which his subjectivistic interpretation of probability had led him. Although this theorem is mentioned in many expositions of the theory of subjective probability, there are not many satisfactory discussions of its significance available to philosophers. (The best one, and almost the only one, is Braithwaite's paper ‘On Unknown Probabilities’.)

You are, I am sure, just as aware as I am that the operational nodes of a complex problem, the points at which it can be split open to yield nuggets of new insight or achieve lasting advances, often lie in tediously technical details perhaps incomprehensible to all but specialists in the matter and anyways totally lacking in the romance and easy excitement which attract the topic's dilettantes. I would like you to hold fast to this appreciation, for the concerns I shall raise here are technical indeed. They are, however, seminal technicalities which, as we seek to fathom them, should fundamentally reshape our comprehension of the logic of confirmation, causal connectedness, and the foundations of statistical inference. In brief, it will be seen that certain powerful everyday intuitions concerning which propositions are confirmationally irrelevant to which others are exceedingly difficult to justify.

A rule for the acceptance of scientific hypotheses called ‘the principle of cost-benefit dominance’ is shown to be more effective and efficient than the well-known principle of the maximization of expected (epistemic) utility. Harvey's defense of his theory of the circulation of blood in animals is examined as a historical paradigm case of a successful defense of a scientific hypothesis and as an implicit application of the cost-benefit dominance rule advocated here. Finally, various concepts of ‘dominance’ are considered by means of which the effectiveness of our rule may be increased.

Orthodox statistical theory, which is the theory used by most practicing statisticians, physicists, biologists, and social scientists, assumes there are objective probabilities which are properties of physical systems. Statistical hypothesis testing is a branch of statistical theory concerned with a theory for accepting or rejecting statements which ascribe these objective probabilities to particular physical systems. Since use of the theory of statistical hypothesis testing leads to the acceptance or rejection of a kind of empirical statement, I shall assume that this theory is a part of inductive logic. Recent philosophical inquiries have largely ignored orthodox statistical theory, and personalistic (or Bayesian) statisticians have attacked it. Since the theory is so widely used, it is important to reexamine its foundations and its place in the canon of inductive logic.

‘Tachyons’ are hypothetical faster-than-light particles. Their existence has been suspected and sought, on the ground that they appear to be compatible with the laws of nature, particularly with Special Relativity, and so there is at least some likelihood that they exist. That last mad inferential leap is justified by the experience of particle physicists, summed up in ‘Gell-Mann's totalitarian principle’ that “whatever is not forbidden is compulsory.” Experimental searches made so far have failed to find them.

The classical reason for ruling out faster-than-light particles has been that according to Special Relativity an infinite force would be required to accelerate a particle up to and beyond the speed of light. For if the particle's rest mass mo is greater than zero, then its relativistic mass, given by the formula

approaches infinity as the particle's velocity v approaches c, the speed of light.

The Einstein-Podolsky-Rosen paradox is an old problem which started back in 1935 with an article in Physical Review titled ‘Does Quantum Mechanics Describe Physical Reality Completely?’ These authors assert that quantum mechanics, being inconsistent, cannot describe physical reality completely. In the present paper the nature of the inconsistency will be analyzed and it will be shown that the E.P.R. paradox is essentially of formal nature and that the apparent formal inconsistency may be regarded as a consequence of unjustifiable presupposition.

According to quantum mechanical theory the states of a microscopic system may be represented by state vectors and in the absence of any disturbance from outside the state vectors will change continuously with time according to Schrodinger's equation.

What is remarkable about the history of atomism is the fact that it can be traced back to the very beginning of human reflection on nature. It is needless to recall the Pythagorean monadism and the names of Leucippus, Democritus and Lucretius: atomism is clearly as old as the first scientific and even proto-scientific explanations of nature. What is even more remarkable is that human thought was able so early and without the aid of microscope and measuring devices to anticipate one of the main findings of modern science. The significance of this anticipation is not diminished by the fact that only the most general features of modern atomism were present in the thought of its ancient ancestors: it was still quite an achievement in the fifth century B.C. to hold the view that space is infinite, that matter is homogeneous and discontinuous in its structure and that all diversity and all changes in nature are reducible to the configurations and displacements of homogeneous, permanent units.

One important view of the nature of facts in science sees the validity of factual claims as resting upon intersubjective agreement through observation, yet the conditions underlying such intersubjectivity are rarely explored. In this paper I should like to inquire into the role of shared method in arriving at intersubjective agreement concerning fact. One useful way of exploring this issue is to examine the methodological element in factual disputes in science, since such controversy may indicate important aspects of factual agreement.

There are times in science when an appeal to factual evidence is successful in the choice between hypotheses. In fact it is clear that, at least on some occasions, there is agreement among scientists as to “what the facts are.” Moreover, such factual agreement can be found between scientists who maintain quite different theories.

The propensity interpretation poses an intriguing alternative to the frequency definition for the explication of probability as a physical magnitude. It is intended to provide an explicitly dispositional account of this concept within the context of statistical laws. First systematically advocated by Karl Popper, it has been endorsed - in one form or another - by Ian Hacking and D. H. Mellor, among others. The purpose of this paper is, first, to distinguish two rather different formulations of the propensity construct (which we shall refer to as the ‘long run’ and ‘single case’ concepts); second, to explain away some of the objections that, prima facie, might be thought to undermine an explication of this kind; and, third, to analyze the inadequacies of a single case dispositional account that fails to take seriously the concept of probability as a statistical disposition.

The Hardware Thesis (HT) is a claim that psychological theories are irreducible to neurological theories; it has its basis in analyses of the distinction between the psychological functions postulated to account for the law-like relations between perceptual input and behavioral output, and the neural structures (or ‘hardware’) which embody these functions. HT's particular commitment to psychology-neurology irreducibility follows from the conjunction of these three assertions:

1. (A) The role of psychological theories is to postulate systems of functions which mediate between perceptual input and behavioral output.

2. (B) The role of neurology is to identify and describe the structures (or ‘hardware’) which embody the functions postulated by psychological theories.

3. (C) Theories postulating systems of functions are not reducible to, or eliminable in favor of, the theories which identify the structures performing or embodying such functions. Generally, theories whose role is limited to the identification of the structures embodying the functions postulated by other theories have little or no explanatory value.

Starting with David Hume, most philosophers have maintained that it is illicit to argue that inductive arguments will be successful in the future because they have been successful in the past. This philosophic tradition claims that such an argument is circular since it is an attempt to prove the principle that the future will resemble the past by means of an inductive argument which principle all inductive arguments presuppose. Hans Reichenbach is such a philosopher but he goes on to add that even though induction can not be so justified, our using induction may be justified. Max Black, on the other hand, may be identified as one of the leaders of the movement which accepts what others deem the circular argument. In this paper the position of Reichenbach and Black will be examined.

Scientific revolutions have been described as episodes in the history of science in which old empirical research activities, standards of achievement, problem fields and even ontologies have been exchanged for new (Kuhn, 1962; Feyerabend, 1962).

Also it has been claimed that rational canons for the evaluation of theories cannot reach across scientific revolutions. The revolutionary new theory can be defended only by rhetorical techniques, not by hypothetico-deductive or other inductive argumentation to or from empirically ascertained evidence. A revolutionary new theory achieves dominance over its predecessor only after the authority sustaining the latter theory is no longer effective. Thus, succeeding theories in scientific revolutions are held to be methodologically incommensurable. That is, logical argumentation cannot be used to assign differential values to succeeding theories.

A superficial examination of what it means for two theories to differ ontologically might lead to the conclusion that theories so differing are methodologically incommensurable.

Kuhn, Feyerabend, Polanyi, and Whorf would at times maintain that scientific objectivity is a myth. Kuhn writes:

He says that he

On the basis of his interpretation of the history of science, Polanyi, also, feels that in a strong sense scientific knowledge is not objective ([11], p. 16). On the basis of his study of widely differing languages Whorf makes a similar claim:

There is in the philosophy of science a view of the nature of science which is often referred to as the orthodox view. In my opinion Dudley Shapere has succinctly characterized the main tenets of this view in his article ‘Meaning and Scientific Change’. According to this view, let me refer to it as the orthodox Logical Empiricist (LE) view, the problem of developing a theory of scientific change was not considered to be a legitimate problem for the philosophy of science. A primary concern of the Logical Empiricist was to analyze the logical structure which is shared by all scientific theories. From the point of view of the development of science the logical structure of scientific theories is a constant. What varies from one theory to another is their empirical content not their logical form.

I would like to make it clear at the outset that this paper is not about a problem in the philosophy of science; it is about the philosophy of science itself. Furthermore, the discussion will not be confined to developments internal to philosophy of science but will include considerations of external factors and their possible relations to the philosophy of science. The justification for this departure from standard practice is simply that the issues to be discussed seem to be enough on many peoples’ minds to justify bringing them out into the public arena.

There is no need to dwell on the all too familiar external factors labeled by well-known catch phrases such as ‘over-population’, ‘pollution’, ‘violence’, ‘runaway technology’, ‘social disintegration’, etc., etc. Although one may debate their precise nature and speculate on their eventual relative significance, the seriousness of these problems, especially in conjunction, can hardly be doubted.

It is hardly news today to report that philosophers of science share a widespread feeling that methods of analysis which have served them well for half a century are reaching the limits of their usefulness. During much of the twentieth century, they have been concentrating on those aspects of science which lend themselves most readily to analysis using the tools of formal logic; they have given detailed, sophisticated accounts of the ways in which the general principles of a natural science are - or might conceivably be - applied to entail statements about its particular phenomena; and they have done much to make clearer the part played in natural science by logical systems. The resulting debate has been complex and on a high level of abstraction: primitive terms, protocol-statements, hypothetico-deductive systems, inductivism … verification, falsification, confirmation, corroboration, refutation ….

In one sense, not every science of social phenomena qualifies as a social science, but only one which investigates the structure of one or more entire societies or cultures. It is within this context, perhaps, that historical linguistics, despite its central concern with an important variety of socially transmitted behavior and its largely deductive character, is less often classified with the social sciences than with the humanities.

From a broader standpoint, however, one may construe as a social science any science which investigates a complex of human behavior, attitude and belief that is transmitted, maintained, modified or discontinued through interpersonal influence. If the social sciences are understood in this broad sense, it is possible to distinguish two kinds of theory at work in them. On one hand, we may discern theories of social phenomena which function in deductive-nomothetic explanation. A typical example is the theory of the evolution of the Indo-European languages.