Bas C. Van Fraassen

G. E. Moore and L. Wittgenstein discussed statements of form “A and I do not believe that A,” and offered quite different diagnoses of the apparent absurdity. I will examine logical aspects of this paradox, including variants for subjective probability as well as simple belief. In the end I will argue that both Moore's and Wittgenstein's diagnoses appear when we treat belief as a modality, provided we give the language both a third-person and first-person reading. In this way a classical modal logic can have a non-classical logic hidden inside.

What is empiricism and what could it be? Bas C. van Fraassen, one of the world’s foremost contributors to philosophical logic and the philosophy of science, here undertakes a fresh consideration of these questions and offers a program for renewal of the empiricist tradition. The empiricist tradition is not and could not be defined by common doctrines, but embodies a certain stance in philosophy, van Fraassen says. This stance is displayed first of all in a searing, recurrent critique of metaphysics, and second in a focus on experience that requires a voluntarist view of belief and opinion._ _Van Fraassen focuses on the philosophical problems of scientific and conceptual revolutions and on the not unrelated ruptures between religious and secular ways of seeing or conceiving of ourselves. He explores what it is to be or not be secular and points the way toward a new relationship between secularism and science within philosophy.

Insight into the methodology of scientific inquiry developed slowly over the preceding century. At issue was the crucial difference between the confirmation of empirical statistical hypotheses, a well-understood subject, and the empirical support for foundational scientific theories. In retrospect, the seminal ideas of the physicist-philosopher Hermann Weyl led, through a series of philosophical debates, to a view of empirical grounding of models and theories. This view disentangles the relation between confirmation and evidential support, and highlights the conditions of practical applicability.

Quantum theory was developed in response to a welter of new experimental phenomena, yet appeared to depict a world so esoteric as to be literally unimaginable. Interpretation of the theory became feasible only after von Neumann's theoretical unification, but von Neumann's own interpretation astonishingly implied that in measurement something happens that violates Schroedinger's equation, the theory's cornerstone. This book argues first of all that the phenomena themselves, without theoretical motives, suffice to eliminate ’common cause’ models, thus requiring a radical departure from classical physics models. The measurement process, however, has an adequate description of itself as a quantum‐mechanical process, so that the theory can be seen as complete in a relevant sense. But the question of interpretation, ‘How could the world possibly be the way this theory says it is?’, is not thereby answered. In response to that question it is argued that the theory admits a plurality of interpretations, each of which helps to understand the theory further, but also advocates one particular interpretation (the Copenhagen Variant of the Modal Interpretation). That interpretation is then applied to such topics as the Einstein–Podolsky–Rosen paradox and the problem of ’identical’ particles, quantum statistics, identity, and individuation.

This book presents an empiricist alternative (‘constructive empiricism’) to both logical positivism and scientific realism. Against the former, it insists on a literal understanding of the language of science and on an irreducibly pragmatic dimension of theory acceptance. Against scientific realism, it insists that the central aim of science is empirical adequacy (‘saving the phenomena’) and that even unqualified acceptance of a theory involves no more belief than that this goal is met. Beginning with a critique of the metaphysical arguments that typically accompany scientific realism, a new characterization of empirical adequacy is presented, together with an interpretation of probability in both modern and contemporary physics and a pragmatic theory of explanation.

Vague subjective probability may be modeled by means of a set of probability functions, so that the represented opinion has only a lower and upper bound. The standard rule of conditionalization can be straightforwardly adapted to this. But this combination has difficulties which, though well known in the technical literature, have not been given sufficient attention in probabilist or Bayesian epistemology. Specifically, updating on apparently irrelevant bits of news can be destructive of one’s explicitly prior expectations. Stability of vague subjective opinion appears to need a more complex model.

The world science describes tends to have a very strange look. We can’t see atoms or force fields, nor are they imaginable within visualizable categories, so neither can we even imagine what the world must be like according to recent physical theories. That tension, between what science depicts as reality and how things appear to us, though it is more striking now, has been with us since modern science began. It can be addressed, and perhaps alleviated by inquiring into how science represents nature. In general, representation is selective, the selection is of what is relevant to the purpose at hand, and success may even require distortion. From this point of view, the constraint on science, that it must ‘save the phenomena’, takes on a new form. The question to be faced is how the perspectival character of the appearances (that is, contents of measurement outcomes) can be related to the hidden structure that the sciences postulate. In the competing interpretations of quantum mechanics we can see how certain traditional ideals and constraints are left behind. Specifically, Carlo Rovelli’s Relational Quantum Mechanics offers a probative example of the freedom of scientific representation

The 1960s saw many revolutions, worldwide, and some of that epoch’s revolutionary spirit manifested itself in philosophy of science, with strong reactions against the dominant “received view” of Logical Positivism. Scientific realism emerged to dispute ontology, Kuhn single-handedly turned our eyes back to history of science, and the semantic approach replaced the methodological framework for philosophers of science. The Logical Positivist revolution had just about reached age 50 at the time; today the semantic approach is about 50 years old as well, and faced with a plethora of new developments. I will discuss how the semantic approach was born, and its fortunes and misfortunes, from its beginnings to approximately 1990, with just a brief look at what has been happening since then.