Bastiaan Cornelis van Fraassen (/væn ˈfrɑːsən/; Dutch: [vɑn ˈfraːsə(n)]; born 5 April 1941) is a Dutch-American philosopher noted for his contributions to philosophy of science, epistemology and formal logic.
[7] Since 2008, van Fraassen has taught at San Francisco State University, where he teaches courses in the philosophy of science, philosophical logic, and the role of modeling in scientific practice.
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.
Focusing on the problem of underdetermination, he argued for the possibility that theories could have empirical equivalence but differ in their ontological commitments.
In his paper "Singular Terms, Truth-value Gaps, and Free Logic",[17] van Fraassen opens with a very brief introduction of the problem of non-referring names.
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.
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.
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".