The overall purpose of this paper is to clarify the physical meaning and epistemological status of the term ‘measurement’ as used in quantum theory. After a review of the essential logical structure of quantum physics. Part I presents interpretive discussions contrasting the quantal concepts observable and ensemble with their classical ancestors along the lines of Margenau's latency theory. Against this background various popular ideas concerning the nature of quantum measurement are critically surveyed. The analysis reveals that, in addition to internal mathematical difficulties, all the so-called quantum theories of measurement are grounded in unjustifiable, classical presuppositions.

It is now commonly accepted that N. Goodman's predicate “grue” presents the theory of confirmation of C. G. Hempel (and other such theories) with grave difficulties. The precise nature and status of these “difficulties” has, however, never been made clear. In this paper it is argued that it is very unlikely that “grue” raises any formal difficulties for Hempel and appearances to the contrary are examined, rejected and an explanation of their intuitive appeal offered. However “grue” is shown to raise an informal, “over-arching” difficulty of great magnitude for all theories of confirmation, including Hempel's theory.

In this paper I attempt to elucidate the nature of that sense of ‘methodology’ which is concerned with the strategics, techniques, and procedures of scientific experimentation. It is claimed that methodology in this sense is at bottom a set of logical relations between sentences expressing pervasive facts of the subject matter and sentences describing experimental behavior. In particular a successful methodology is one in which the set of these sentences is logically consistent. I then turn to the problems involved in teaching and learning an explicit methodology. Finally, I argue that this analysis throws fresh light on the distinction between knowing a fact and possessing a skill or competence.

Controversy over the adequacy of the regularity or covering law theory of explanation when applied to historical actions continues to rage. A detailed analysis is here made of Professor A. Donagan's recent attack on this theory, as representative of many others. His alternative model of deductive non-law explanation, based on Popper's notion of the “logic of the situation,” is then shown to be invalid and generally defective. Finally, four sources of the difficulty are elicited which, when resolved, provide support for the regularity theory in its probabilistic version. We suggest that this theory, despite recent criticism, can be fruitfully extended to historical explanation by uncovering and codifying a major difference between history and science, the rational actions of historical agents, without distorting it.

In his article [5], Brian Skyrms adduces (on p. 233) some generalizations which, he claims, receive no confirmatory support from their positive instances even though all the predicates they contain are well entrenched in Goodman's sense. Invoking the principle that “a generalization is lawlike if it is capable of receiving confirmatory support from its positive instances” (p. 232; actually, the converse is needed and, I will assume, intended by him), he claims that his examples “provide striking demonstration of the fact that the lawlikeness of a hypothesis is not a simple function of the projectibility of its constituent predicates.” I think the claim is of great interest; but I will try to show that Skyrms's argument fails to establish it because it presupposes an unwarranted assumption which raises a problem of general importance for confirmation theory.

According to Hempel, all scientific explanations and predictions which are produced exclusively with deterministic laws must be deductive, in the sense that the explanandum or the prediction must be a logical consequence of the laws and the initial (and boundary) conditions in the explanans. This deducibility thesis (DT) has been attacked from several quarters. Some time ago Canfield and Lehrer presented a “refutation” of DT as applied to predictions, in which they tried to prove that “if the deductive reconstruction [DT for predictions] were an adequate reconstruction, then scientific prediction would be impossible” ([2], p. 204). Their argument seems to have been uncontested except for an inconclusive rejoinder by Beard (cf. [1]). Moreover, Stegmüller has recently argued that “it may turn out that all or at least most of the so-called deductive-nomological explanations are in truth inductive and not deductive arguments, in view of the difficulty which has been pointed out by Canfield and Lehrer” ([3], p. 7). It seems it would be worth investigating whether Canfield and Lehrer's argument is, indeed, correct.

Abner Shimony called it coherence; John Kemeny called it strict fairness; today many people speak of strict coherence. According to Shimony's definition, a set of betting rates on a series of propositions hi and ei is strictly incoherent, when “there exists a choice of stakes Si such that, if X accepts the series of bets at these stakes, then no matter what the actual truth values of hi, and ei may be, X can at best lose nothing, and in at least one possible eventuality he will suffer a positive loss” ([3], p. 9).

An intuitive idea concerning degrees of precision is widely accepted, and it is that we increase precision of theories by paying attention to ever decreasing orders of magnitude of measurements which we incorporate in these theories. We increase precision of measuring or of predicting measurement of length, for instance, if we pay attention not only to centimeters but also to millimeters, microns, angstroms, and so on. And our theories are precise to centimeters, then to millimeters, and so on respectively. The idea is that increased precision is the process of capturing a point within nested intervals, and that this is reflected both in experimental and in theoretical progress. An intuitive analogy may be drawn with series of photos made by a camera which approaches the moon's surface. A corollary from this intuitive idea which has been stated by a number of writers is that observation reports and theories are not overthrown even when superseded by more accurate observation because within the limits of their own precision-range they are still valid. When a law in physics is stated, it is stated usually without such qualifications; but this is a mere matter of convenience, we are told. The idea is that a tacit proviso is understood and the law should be understood to be not the statement “such and such is the case” but the statement “within this and that limit of accuracy such and such is the case”; in such a formulation, the law, once verified, remains unshaken regardless of further progress in the field.