A Dirac-like equation for a massive field obeying the classical Proca equations of motion (PMO) is proposed in close analogy with Majorana’s construct for Maxwell electrodynamics. Its underlying algebraic structure is examined and a plausible physical interpretation is discussed. The behavior of the PMO equations in the presence of an external electromagnetic field is also investigated in the low energy limit, via unitary transformations similar to the Foldy-Wouthuysen canonical transformation for a Dirac fermion.

What considerations place genuine constraints on an adequate semantics for normative and evaluative expressions? Linguists recognize facts about ordinary uses of such expressions and competent speakers’ judgments about which uses are appropriate. The contemporary literature reflects the widespread assumption that linguists don’t rely upon an additional source of data—competent speakers’ judgments about possible disagreement with hypothetical speech communities. We have several good reasons to think that such judgments are not probative for semantic theorizing. Therefore, we should accord these judgments no (...) probative value for the development of a semantics for our moral terms. Such judgments can no longer be presumed to put pressure on theories according to which our moral expressions share a semantics with ordinary, descriptive terms. Many rivals to pure, Descriptivist theories count among their advantages the ability to accommodate these judgments. If these judgments have no probative value, such theories lose an important source of support. (shrink)

Historians of seventeenth-century science have frequently asserted that Kepler's laws of planetary motion were largely ignored between the time of their first publication and the publication of Newton's Principia . In fact, however, they were more widely known and accepted than has been generally recognized.Kepler's ideas were, indeed, rather slow in establishing themselves, and until about 1630 there are few references to them in the literature of the time. But from then onwards, interest in them increased fairly rapidly. In particular, (...) the principle of elliptical orbits had been accepted by most of the leading astronomers in France before 1645 and in England by about 1655. It also received quite strong support in Holland.The second law had a more chequered history. It was enunciated in its exact form by a few writers and was used in practice by some others without being explicitly formulated, but the majority, especially after 1645, preferred one or another of several variant forms which were easier to use but only approximately correct. The third law attracted less interest than the others, chiefly perhaps because it had no satisfactory theoretical basis, but it was correctly stated by at least six writers during the period under review.Between about 1630 and 1650 Kepler's Epitome Astronomiae Copernicanae was probably the most widely read work on theoretical astronomy in northern and western Europe, while his Rudolphine Tables, which were based upon the first two laws, were regarded by the majority of astronomers as the most accurate planetary tables available.Kepler's work certainly did not receive all the recognition it deserved, but the extent to which it was neglected has been much exaggerated. (shrink)

In this brief reply I argue that criticisms of the hiddenness argument recently published in this journal by Imran Aijaz and Markus Weidler are without force. As will be shown, their critique of my conceptual version of the argument misses the mark by missing crucial distinctions. Their critique of my analogical version of the argument misunderstands that argument and also misapplies the work of W. H. Vanstone. And their critique of my view that belief is necessary for a certain kind (...) of relationship with God overlooks both some central features of that kind of relationship and some good reasons for not accepting acceptance or anything similarly nonbelieving as a substitute for belief in this context. (shrink)

Our goal here is to help identify the contextualist’s most worthy competitor to relativism. Recently, some philosophers of language and linguists have argued that, while there are contextualist-friendly semantic theories of deontic modals that fit with the relativist’s challenge data, the best such theories are not Lewis-Kratzer-style semantic theories. If correct, this would be important: It would show that the theory that has for many years enjoyed the status of the default view of modals in English and other languages is (...) in need of revision. Here we defend the default view by showing how a Kratzer-style semantics is able to make available readings of the relevant utterances that fit with the pretheoretical judgments opponents purport it cannot fully capture. Having established this, we turn to considering the more theoretical grounds proponents have offered for preferring their rival contextualist views. Here the question is to what extent such grounds favor semantic over what Korta and Perry call “near-side pragmatic” explanations of our judgments. In particular, we argue that our favored readings figure in near-side pragmatic explanations of those judgments that possess the methodological and theoretical advantages of systematicity and unity at least as well as, if not to a greater extent than, those of opponents who argue for their revised semantic theories on the basis of these advantages. (shrink)

The contributions in the first part Re-modelling logic of this volume take account of formal logic in the theory of rational argumentation.

The numerous researches devoted to 'jaundice' during the Second World War have brought to light the existence of an infectious type of hepatic jaundice or 'homologous serum jaundice' following parenteral injection of vaccines containing human serum and blood transfusions, which were carried out on a large scale at the time. This type of serum jaundice was then gradually differentiated from 'catarrhal', contagious or epidemic jaundice by clinical trials along with large series of animal studies. Finally, the epidemiological, clinical and biological (...) data obtained made it possible to establish, between 1944 and 1954, the viral etiology of these two types of jaundice: the A virus, present in the patients' blood and stools, was considered to be the agent responsible for epidemic hepatitis; the B virus, present primarily in the blood, was held to be responsible for serum hepatitis. (shrink)

Genealogía y lógica de la ratio imperial romana -- Racionalización ética judía y religión de salvación cristiana -- La revolución teológica de Pablo y sus consecuencias -- Teología política imperial y militancia cristiana -- La teología trinitaria y el destino de la teología imperial -- Hilario, Ambrosio y el camino del catolicismo en Occidente -- Mal y salvación: Augstín de Hipona.

Physical arguments stemming from the theory of black-hole thermodynamics are used to put constraints on the dynamics of closed-string tachyon condensation in Scherk–Schwarz compactifications. A geometrical interpretation of the tachyon condensation involves an effective capping of a noncontractible cycle, thus removing the very topology that supports the tachyons. A semiclassical regime is identified in which the matching between the tachyon condensation and the black-hole instability flow is possible. We formulate a generalized correspondence principle and illustrate it in several different circumstances: (...) an Euclidean interpretation of the transition from strings to black holes across the Hagedorn temperature and instabilities in the brane-antibrane system. (shrink)

Conference held June 1990 under the auspices of the Israel Academy of Sciences and Humanities and the Hebrew University of Jerusalem.