The perturbative approach to quantum field theory has long been viewed with suspicion by philosophers of science. This article offers a diagnosis of its conceptual problems. Drawing on Norton’s discussion of the notion of approximation I argue that perturbative QFT ought to be understood as producing approximations without specifying an underlying QFT model. This analysis leads to a reassessment of common worries about perturbative QFT. What ends up being the key issue with the approach on this picture is not mathematical (...) rigour, or the threat of inconsistency, but the need for a physical explanation of its empirical success. 1Three Worries about Perturbative Quantum Field Theory2The Perturbative Formalism 2.1Expanding the S-matrix2.2Perturbative renormalization3Approximations and Models4Perturbative Quantum Field Theory Produces Approximations5The Real Problem. (shrink)

Providing a precise statement of their position has long been a central challenge facing the scientific realist. This paper draws some morals about how realism ought to be formulated from the renormalization group framework in high energy physics.

The orthodox characterization of spontaneous symmetry breaking in statistical mechanics appeals to novel properties of systems with infinite degrees of freedom, namely, the existence of multiple equilibrium states. This raises the same puzzles about the status of the thermodynamic limit fueling recent debates about phase transitions. I argue that there are prospects of explaining the success of the standard approach to SSB in terms of the properties of large finite systems. Consequently, despite initial appearances, the need to account for SSB (...) phenomena does not offer decisive support to claims about the explanatory and representational indispensability of the thermodynamic limit. (shrink)

"Mentoring the Mentor" recreates a Freirian dialogue in a printed format. In this volume, sixteen distinguished scholars engage in a critical and thoughtful exchange with Paulo Freire. While some contributors voice appreciation for Freire's ideas and for what it means to -reinvent Freire- in a North American context, others offer sharp critiques of Freire's philosophy and, of equal importance, of the various interpretations of his work. A variety of chapters describe specific uses which have been made of Freire's ideas in (...) diverse educational contexts, from the New York City public schools to the revolutions in Guinea Bissau and Eritrea. Finally, Paulo Freire himself responds to the major issues which are raised in the volume and invites readers to share in a continuing lively dialogue about the meaning of democratic and revolutionary education. -The fundamental task of the mentor is a liberatory task. It is not to encourage the mentor's goals and aspirations and dreams to be reproduced in the mentees, the students, but to give rise to the possibility that the students become the owners of their own history. This is how I understand the need that teachers have to transcend their merely instructive task and to assume the ethical posture of a mentor who truly believes in the total autonomy, freedom, and development of those he or she mentors.- (from Chapter Sixteen, -A Response- by Paulo Freire)". (shrink)

In this article, we offer a detailed study of two important episodes in the early history of high-energy physics, namely the development of the Chew and the Nambu-Jona-Lasinio models. Our study reveals that both models resulted from the combination of an old Hamiltonian, which had been introduced by earlier researchers, and two new approximation methods developed by Chew and by Nambu and Jona-Lasinio. These new approximation methods, furthermore, were the key component behind the models’ success. We take this historical investigation (...) to support two philosophical theses about the manner in which scientific modelling operates in high-energy physics. Both of these theses run counter to a view that is commonly accepted among philosophers of science: the view that all approximations can be embedded within an equivalent idealized system, and that whatever role the former might play in scientific modelling is therefore parasitic on the much more substantial work performed by the latter. Our first thesis, which we call “Distinctness,” states that approximation methods constitute an independent category of theoretical output from idealized systems. We thus believe that approximations and idealized systems constitute two independent types of objects, both of which are essential to the practice of modelling. Our second, more radical thesis is called “Content Determination.” Our claim here is that approximation methods can in fact be essential to assigning determinate physical content to the idealized systems with which they jointly operate. As we show, this is due to the fact that quantum field theory allows for a very thin characterization of idealized systems only, making the use of approximations necessary to supply additional content. We conclude the paper with a few reflections about the manner in which our two theses can be used to articulate David Kaiser’s views on the “vanishing of scientific theory” in physics after WWII. (shrink)

Decisions about long-term ventilation in children can be clinically contentious and ethically challenging. In this article, the relevant legal, professional and moral principles inherent in such cases are explored. We commend the central importance of deliberation in the assessment of best interests, and propose a practical framework to assist the parent–clinical team to reach decisions in as transparent and equitable a manner as possible.