Philosophy of science

Van Fraassen coined the term "constructive empiricism" in his 1980 book The Scientific Image, in which he argued for agnosticism about the reality of unobservable entities. That book was "widely credited with rehabilitating scientific anti-realism."^[16] According to the Stanford Encyclopedia of Philosophy:

The constructive empiricist follows the logical positivists in rejecting metaphysical commitments in science, but parts with them regarding their endorsement of the verificationist criterion of meaning, as well as their endorsement of the suggestion that theory-laden discourse can and should be removed from science. Before van Fraassen's The Scientific Image, some philosophers had viewed scientific anti-realism as dead, because logical positivism was dead. Van Fraassen showed that there were other ways to be an empiricist with respect to science, without following in the footsteps of the logical positivists.^[16]

Paul M. Churchland, one of Van Fraassen's critics, contrasted Van Fraassen's idea of unobservable phenomena with the idea of merely unobserved phenomena.^[17]

In his 1989 book Laws and Symmetry, Van Fraassen attempted to lay the ground-work for explaining physical phenomena without assuming that such phenomena are caused by rules or laws which can be said to cause or govern their behavior. Focusing on the problem of underdetermination, he argued for the possibility that theories could have empirical equivalence but differ in their ontological commitments. He rejects the notion that the aim of science is to produce an account of the physical world that is literally true and instead maintains that its aim is to produce theories that are empirically adequate.^[18] Van Fraassen has also studied the philosophy of quantum mechanics, philosophical logic, and Bayesian epistemology.

Philosophical logic

Van Fraassen has been the editor of the Journal of Philosophical Logic and co-editor of the Journal of Symbolic Logic.^[8]

In logic, Van Frassen is best known for his work on free logic and his introduction of the supervaluation semantics. In his paper "Singular Terms, Truth-value Gaps, and Free Logic",^[19] Van Fraassen opens with a very brief introduction of the problem of non-referring names.

Instead of any unique formalization, though, he simply adjusts the axioms of a standard predicate logic such as that found in Willard Van Orman Quine's Methods of Logic. Instead of an axiom like ${\displaystyle \forall x\,Px\Rightarrow \exists x\,Px}$ he uses ${\displaystyle (\forall x\,Px\land \exists x\,(x=a))\Rightarrow \exists x\,Px}$; this will naturally be true if the existential claim of the antecedent is false. If a name fails to refer, then the atomic sentence containing it can be assigned a truth value arbitrarily, provided that it is not an identity statement. Free logic is proved to be complete under this interpretation.

He indicates that, however, he sees no good reason to call statements which employ them either true or false. Some have attempted to solve this problem by means of many-valued logics; Van Fraassen offers in their stead the use of supervaluations. Questions of completeness change when supervaluations are admitted, since they allow for valid arguments that do not correspond to logically true conditionals.

His paper "Facts and tautological entailment" (J Phil 1969) is now regarded as the beginning of truth-maker semantics.

Bayesian epistemology

In "Belief and the Will", Van Fraassen proposed what is now known as Van Fraassen's reflection principle: "to satisfy the principle, the agent's present subjective probability for proposition A, on the supposition that his subjective probability for this proposition will equal r at some later time, must equal this same number r".^[20] Within Bayesian epistemology this principle is recognized as an important synchronic norm; however Van Fraassen points out that a Dutch Book argument can be made against the principle.^[21][22]