Quantum electrodynamics is the theory of electrons and other elementary charged particles, interacting through the exchange of light quanta. Albert Einstein introduced the light quantum in 1905, but for about three decades physicists applied quantum ideas mainly in theories of the structure and behavior of matter, not to electromagnetic radiation itself, which was always treated semi-classically. This began to change after 1923 with the discovery of the Compton effect and its kinematic description by Arthur Compton and Peter (...) Debye, based on the light quantum. In this paper we review the study of high-energy radiation that led to Compton's discovery. We discuss the analysis of the intensity distribution of Compton-scattered radiation that together with the ''new'' quantum theory beginning in 1925, resulted in the development, especially by Pascual Jordan and Paul Dirac, of a quantum theory of electromagnetic radiation in interaction with matter. (shrink)

PORTUGUESE: Neste artigo, apresentaremos uma visão particular do desenvolvimento de teorias científicas que denominamos (inspirados em Ortega y Gasset) "perspectivismo". Discutiremos como, através desse enfoque, é possível compatibilizar diversas descrições aparentemente distintas e incompatíveis de uma suposta realidade que se investiga. Fazemos isso distinguindo entre a "realidade" (R) e a "descrição empírica da realidade" (Re). Aceitando que podemos ter diversas descrições empíricas de uma mesma realidade, discutimos o caso particular em que esse esquema é utilizado nos debates atuais acerca da (...) ontologia da física quântica, em especial da mecânica quântica não relativista. Como se sabe, essa teoria é compatível com distintas ontologias (ou metafísicas), em particular, pode ser vista como comprometida com uma ontologia de indivíduos, mas também com uma ontologia de não indivíduos. Ambas as alternativas são plausíveis e merecem ser desenvolvidas. Propomos que o perspectivismo aqui apresentado é neutro com relação à escolha de uma metafísica (ontologia), bem como aos debates entre realistas e antirrealistas em filosofia da ciência. Concluímos que passar do pluralismo aceito pelo perspectivista ao realismo ou antirrealismo envolve comprometimento com teses mais robustas acerca da relação entre realidade e descrição da realidade. ENGLISH: In this article we present a particular view of the development of scientific theories which (following Ortega y Gasset), we term "perspectivism". Making use of this view, we discuss how we can accommodate distinct and apparently incompatible descriptions of a supposed reality under investigation. We distinguish between a "reality" (R) and its "empirical description", (Re). Acknowledging that we can have diverse empirical descriptions of the same reality, we discuss the particular case in which the view is applied to current debates on the ontology of quantum physics, especially of non-relativistic quantum mechanics. As it is well known, this theory is compatible with treating quantum objects either as individuals or as non-individuals. Both ontologies are possible and deserve to be developed. We propose that the perspectivism developed here is neutral not only with respect to the choice of an ontology, but also concerning the debates among realists and anti-realists in the philosophy of science. We conclude that to go beyond the pluralism accepted by perspectivism, and to adopt realism or anti-realism, involves commitment to strong theses about the relation between reality and its descriptions. (shrink)

We review the history of the road to a manifestly covariant perturbative calculus within quantum electrodynamics from the early semi-classical results of the mid-twenties to the complete formalism of Stueckelberg in 1934. We choose as our case study the calculation of the cross-section of the Compton effect. We analyse Stueckelberg's paper extensively. This is our first contribution to a study of his fundamental contributions to the theoretical physics of the twentieth century.

Thomas S. Kuhn’s theory of normal science (NS), aside from being a provocative philosophical reconstruction of the relatively conservative phase of scientific research, contains useful ideas for systematic analysis of specific episodes in the history of science. Therefore, although the theory has been looked at from different angles since the first edition of The Structure of Scientific Revolutions (TSSR) was published in 1962, its detailed exploration of the cumulative phase of research in mature science is of abiding relevance in the (...) philosophy of science. This is because NS provides a compelling account of how and why members of scientific communities succeed, largely, to produce reliable knowledge about an incompletely known phenomenal world. Again, the theory elucidates special features of scientific research that differentiate it from other creative enterprises. In that regard, this paper reconstructs Arthur Compton’s research into x-ray scattering as a good instantiation of NS. Discussion of Compton’s convincing demonstration of the particulate properties of electromagnetic radiation within the framework of NS showcases the elucidatory power of Kuhn’s theory with respect to selected episodes in science, and corroborates the notion that the bulk of scientific work is a conservative puzzle-solving activity with the potential for precipitating scientific revolutions. To the best of my knowledge, this is the first time that Compton’s groundbreaking work on x-ray scattering has been analysed within the framework of Kuhn’s philosophy of science. (shrink)

A new method for obtaining lower bounds on the computational complexity of logical theories is presented. It extends widely used techniques for proving the undecidability of theories by interpreting models of a theory already known to be undecidable. New inseparability results related to the well known inseparability result of Trakhtenbrot and Vaught are the foundation of the method. Their use yields hereditary lower bounds . By means of interpretations lower bounds can be transferred from one theory to another. Complicated machine (...) codings are replaced by much simpler definability considerations, viz., the kinds of binary relations definable with short formulas on large finite sets. Numerous examples are given, including new proofs of essentially all previously known lower bounds for theories, and lower bounds for various theories of finite trees, which turn out to be particularly useful. (shrink)

This investigation addresses the hypothesis that negative affect is associated with decreased ability to shift attention to a new focus. Thirty-nine participants completed a covert attentional orienting task and then viewed a distressing film clip. Mood was measured by self-report at the beginning and end of the session. Correlations between attentional orienting performance and self-reported mood indicated that participants with greater response time costs on invalidly cued trials reported more negative affect in response to the film. These results support the (...) hypothesis that negative affect is associated with a slowness to disengage attention. (shrink)

A great physicist, winner of the Noble Prize in 1927, here gives his views of man’s place in the world. His position is unmistakable and he states it with clarity and vigor. Mankind, in the author’s opinion, is far from a creature who fundamentally obeys inevitable laws; the universe is fundamentally unpredictable and man is fundamentally free.

We investigate whether female board representation and firms’ financial performance are related and whether the relationship differs for firms located in more prejudicial environments. As a proxy for prejudicial environment, we use two geographical indicators: whether a firm is headquartered in a conservative “red” state or in a liberal “blue” state and whether the firm is located in regions where residents possess more stereotypical attitudes about gender equality. We find that both financial performance and female board representation are lower for (...) firms headquartered in red states when compared to those in blue states, and we find similar results for firms located in regions where residents hold more gender-stereotypical views. However, financial performance improves when female directors are present regardless of the firm’s location. Evidence also shows that the incremental improvement in performance measured by Tobin’s q is greater in red-state than in blue-state companies and in regions where residents hold more gender-stereotypical views. The overall results imply that gender stereotyping holds back financial performance and that female directors help improve financial performance. (shrink)

Despite Platonism's unquestioned claim to being one of the most influential movements in the history of philosophy, for a long time the conventional wisdom was that Platonists of late antiquity, or Neoplatonists, were so focused on otherworldly metaphysics that they simply neglected any serious study of the sensible world, which after all is 'merely' an image of the intelligible world. Only recently has this conventional wisdom begun to be dispelled. In fact, it is precisely because these thinkers did see the (...) sensible world as an image of the intelligible world that they devoted so much time and energy to understanding its inner workings. Thus we find Neoplatonists writing on embryology, physiology, meteorology, and astronomy, among other subjects.Neoplatonism and the Philosophy of Nature collects essays by leading international scholars in the field which shed new light on how the Neoplatonists sought to understand and explain nature and natural phenomena. It is thematically divided into two parts, with the first part--The General Metaphysics of Nature--directed at the explication of central Neoplatonic metaphysical doctrines and their relation to the natural world, and the second part--Platonic Approaches to Individual Sciences--showing how these same doctrines play out in individual natural sciences such as elemental physics, geography, and biology. Together these essays show that a serious examination of Neoplatonic natural philosophy has far-reaching consequences for our general understanding of the metaphysics of Platonism as well as for our evaluation of their place in the history of science. (shrink)

A CONCERN TO UNDERSTAND THE POSSIBILITIES AND LIMITS of human freedom is as old as philosophy. Yet the question whether and in what sense human beings are free agents still provokes heated debate. Even a century ago, as William James began his discussion of the issue, he wondered, with some bemusement, whether there could possibly be any “juice” left in it! Happily, he concluded that there was still more to be said, but his eloquent defense of free will failed to (...) convince; it became just another chapter in the ongoing and seemingly endless dispute. In the years since, many additional essays and books have been written, covering every aspect and espousing every possible view of the matter. The deep disagreements continue. It is this very phenomenon, the remarkable persistence—and resistance—of the problem of freedom, upon which I wish to reflect. Why is it that after such a long history the same vigorous differences endure? Is it more than mere philosophical partisanship that keeps the discussants talking past one another? I believe that there is more to it. I suspect, much as Kant thought, that there is here a sort of antinomy in which valid but seemingly incompatible intuitions are expressed over and over again. Perhaps by considering this possibility we can, even now, squeeze out a bit more juice. (shrink)

In an interesting passage in the Philebus , Plato associates pure beauty with geometrical forms created by certain measuring tools used both by mathematicians and carpenters. The ‘beauty of figures’ is analysed as' something straight [εθ τι]… and round [περιφερς] and the two- and three-dimensional figures generated from these by [τρνοι] and ruler [κανσ7iota;] and set-squares [γωναι]' He continues: ‘For I maintain that these things are not beautiful in relation to something, as other things are, but they are always beautiful (...) by nature, by themselves…’. (shrink)

PHILOSOPHY of nature is not currently considered standard fare in philosophy. Rather than the title of an area of inquiry, it has become the name of an isolated historical phenomenon—the Naturphilosophie of Schelling, Goethe, and Hegel, or a label for some school doctrine—the continuing tradition built upon the first books of Aristotle’s Physics or the newer one rooted in Whitehead’s Process and Reality. Philosophers do not typically see these systems of thought in terms of a common problematic, certainly not one (...) which is presently viable or important. (shrink)

This article explores how the Crash Course video series are being used as a content-focused resource in the social studies classroom. It argues that the Crash Course series, alongside its YouTube competitors, has significantly stepped in to fill a vacuum left by criticisms and the unpopularity of lectures, textbooks, and feature films. With over 15 million subscribers and accumulated views over 1.9 billion, Crash Course has become an important and ubiquitous force in history and social studies classrooms and represents a (...) new genre of educational media found on YouTube. However, the dramatic rise in the popularity of educational videos online has not coincided with a growth in educational research, particularly in social studies and history education. This article explores the findings of a mixed-methods study that examines how and why history and social studies teachers are using Crash Course videos in their teaching and planning. In particular, it analyses descriptive statistics derived from the results of a teacher survey ( n = 181) and semi-structured interviews with seven social studies teachers who have used Crash Course in their classrooms. The authors found that teachers in the study are regularly using the Crash Course video series to deliver content which is clearly meeting a need many social studies teachers have. The videos–short, easily accessible, and fun–fit nicely with demands to keep students engaged, reduce reliance on textbooks, and explore new content that teachers have little time to learn themselves. This study also found that rarely, if ever, are teachers inviting students to evaluate or assess the content, trustworthiness, or perspective of Crash Course videos. This article discusses what is gained and what are the risks of embracing Crash Course in the social studies and history classroom. (shrink)

Preface, by F. L. Windolph.--A modern concept of God, by A. H. Compton.--The immortality of man, by J. Maritain.--The idea of God in the mind of man, by M. Royden.--Psychical research and the life beyond death, by H. Hart.--Religion and modern knowledge, by R. Niebuhr.--Immortality in the light of science and philosophy, by W. E. Hocking.--"To whom shall ye liken God?" By C. E. Park.--Man's destiny in eternity, by W. L. Sperry.--The idea of God as affected by modern knowledge, (...) by F. S. C. Northrop. (shrink)

Marjorie Grene's work expresses the conviction that what is called "the new philosophy of science" will not become viable until it is rooted in an understanding of the knower and the known which breaks with the familiar Cartesian dualisms. In order to provide this understanding, she has sought to restore central significance to the phenomenon of life -- to the distinctive ways in which animals, including human beings, perceive and act in their worlds. It is argued that her fundamental premise (...) is that humans, as living beings, bring a shared experience of the world with them into scientific activity. On this basis, she is able to show how scientific objectivity may be seen as a form of pre-scientific exploration and how the scientifically known world may be seen as the pre-scientific life-world interpreted and enriched in scientific terms. (shrink)