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.