Constructive Empiricism

Constructive empiricism is the anti-realist philosophy of science developed by Bas van Fraassen in The Scientific Image (1980). The position holds that science aims at empirical adequacy — theories that correctly describe observable phenomena — rather than truth about unobservable entities. A constructive empiricist accepts a theory as empirically adequate if it 'saves the phenomena': if what it says about observable things and events is true. She does not commit to the reality of the theoretical entities the theory posits — electrons, quarks, fields — because those entities lie beyond the observable. The position is not instrumentalism: van Fraassen allows that theoretical claims have truth values; he simply claims that rational acceptance of a theory does not require belief in those truth values. The constructive empiricist's acceptance is epistemic voluntarism: she is entitled to suspend judgment about the unobservable while fully endorsing the theory's observable consequences. The position faces the challenge that the observable/unobservable distinction is theory-dependent and draws the line differently as technology improves — a bacterium is unobservable to the naked eye but observable under a microscope, and van Fraassen's response to this challenge remains disputed in philosophy of science.