Bas C. van Fraassen

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Identity over time: objective, subjective

. B. van Fraassen and I. Peschard , Go to article in Philosophical Quarterly 2008.
In philosophy of science, identity over time emerges as a central concern in two guises: as an ontological category in the interpretation of physical theories, and as a problem in epistemology with respect to the conditions of possibility of knowledge. In Reichenbach's and subsequent writers on the problem of indistinguishable particles in quantum physics we see the return of a contrast between Leibniz and Aquinas on the subject of individuation. The possibility that the principle of the identity of indiscernables can be rejected has certain logical difficulties, which inexorably lead us from ontology into epistemology.
          For the epistemological problem we must attend to the differences that emerged between the (neo-)Kantian and logical empiricist traditions, also most saliently displayed in Reichenbach's writings. After an examination of the contrast between Kant's and Leibniz' conceptions of empirical knowledge, specifically with respect to the irreducibility of spatio-temporal determinations, we explore an application of a neo-Kantian view to that same problem of indistinguishable particles in physics.

Laws and Symmetry

Synopsis (book):

Laws and Symmetry has three main objectives. The first is to show the failure of philosophical accounts of laws of nature. The second is to undercut the epistemological principles at work in arguments for the reality of laws of nature. The third objective, nearest to my heart, is to be constructive as well, and to contribute to an epistemology and a philosophy of science antithetical to such metaphysical notions as laws of nature. Part One, in which the first objective is pursued, was the main subject of discussion in the symposium to follow. In this Synopsis, therefore, I shall concentrate on that.

In my view, as presented in Chapter 1, the concept of a law of nature is an anachronism, its proper life belonging to the 17th and 18th Centuries. Laws of nature played an important role in the philosophical-scientific thinking of Descartes and Newton, and functioned for them as a central clue to the structure of science. At the same time, two developments threatened the status of law. One was the empiricist critique of necessity and causality, notions closely allied to that of law. The other was that science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and methods foreign to metaphysics. Pre-eminent here is the birth of the symmetry argument. (Discussion of this subject is begun in Chapter 1 and continued in Chapters 10, 11 and 12.) Modern physics argues from symmetry and continuity -- not from universality or necessity, natural kinds or essences, contingency or accident. The concept of a law of nature is a vestigial concept in contemporary science.

Chapter 2 collects the cluster of criteria for what laws must be and do, which are honored in the literature to some degree or other. We can divide the criteria to be met by any philosophical account of laws roughly into major requirements and secondary ones. The major criteria concern what I call the problems of inference and identification. The accounts must show that there is a valid inference from what laws there are to what regularities there are in the world. The account must also identify the relevant aspects of the world that constitute or give rise to its laws, if any. Typically these two tasks lead to a dilemma. If laws of nature are identified in terms of some sort of necessity in nature which is simply postulated as fact, then there is no logical reason to think that the inference from lawlike necessity to actuality is valid. (Calling the postulated factor "necessity" or "necessitation" does not help.) If on the other hand the semantic account of law statements is so constructed that the inference in question is logically valid, then typically the truth-conditions of law statements involve something unidentifiable. Chapters 3, 4, and 5 argue that leading contemporary attempts (by David Lewis, David Armstrong, and a host of others) fail to slip between the horns of this dilemma. Nor do they meet secondary criteria, such as showing that what they make out to be laws of nature are the targets reached, or even aimed for, in scientific inquiry.

Both Quine and Rorty have, in their different ways, proclaimed the death of epistemology. I think they are right about mainstream traditional epistemology. There Induction has given way to Inference to the Best Explanation (IBE) in the epistemology hospitable to realism, or to metaphysics in general. In my view, developed in Part Two, neither Induction nor IBE qualifies as a rational strategy for change of opinion. To that extent at least I endorse some of Quine's and Rorty's conclusions. But it also seems to me that the underground river of probabilism, slowly growing in force over three centuries, has burst forth above ground in the twentieth century and brought new hope for epistemology. In Part Two I argue that with the end of foundationalism, probabilism provides the framework for a new epistemology, which is also adequate for philosophy of science.

The remainder of the book (Chapters 8-13) is devoted to contributions to the semantic approach in philosophy of science, to support my call to leave metaphysics behind. The semantic approach does not require an anti-realist or anti-metaphysical stance. In fact it is also followed by philosophers with very different philosophical positions from my own. But that is just the point: this collaboration in philosophy of science is possible because the approach is in itself neutral, and does not presuppose metaphysical views. I will leave the details aside, since the present symposium concentrates on Part One, which was meant to be the destructive prelude to this constructive effort in philosophy of science.

For current availability, Laws and Symmetry

The Manifest Image and the Scientific Image

pp. 29-52 in D. Aerts (ed.). Einstein Meets Magritte: The White Book -- An Interdisciplinary Reflection. Dordrecht: Kluwer, 1999.

To read this on the web, go to "The Manifest Image and the Scientific Image"


There are striking differences between the scientific theoretical description of the world and the way it seems to us. The consequent task of relating science to 'the world we live in' has been a problem throughout the history of science. But have we made this an impossibility by how we formulate the problem? Some say that besides the successive world-pictures of science there is the world-picture that preceded all these and continues to exist by their side, elucidated by more humanistic philosophers. Wilfrid Sellars codified this conviction in his dichotomy of scientific image and manifest image. Others say that all our world-pictures are transient, evolve, conflict with and replace each other, undergo violent revolutions as well as periods of normal development, and may be incommensurable, allowing of no meaningful dialogue. All such formulations may themselves be tendentious metaphysics, full of false contrasts. Insistence on a radical separation between science and what we have apart from science, on the impossibility of accommodating science without surrender, may be a way of either idolizing or demonizing science rather than understanding it.

Putnam's Paradox: Metaphysics Revamped and Evaded

in Philosophical Perspectives,vol. 11 (Boston: Blackwell, 1997), pp. 17-42.

To read this paper on the Web, go to "Putnam's Paradox"


In Putnam's paper "Realism and Reason" he gave an argument ("the model theoretic argument" it is sometimes called) which he intended as a refutation of metaphysical realism. Unfortunately it seemed to leave everyone, realists or not, in a difficult position. David Lewis called the argument "Putnam's paradox" and advanced a solution (also suggested by Gary Merrill): a bit more realism about the structure of the world or of nature will block the argument. In this way Putnam's argument was turned into putative support for a brand of realism, supposedly the only means to escape its apparently disastrous implications. I offer a different reading of the argument, with a non-realist escape from paradox as well as an (unsympathetic) diagnosis of the realist response.

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