Subjectivism

Abstract

This essay discusses subjective probability—its foundations, justification, and relation to other subjects, such as decision theory and confirmation theory. Various forms of subjectivism (the belief in subjective probability) are described, and distinguished from non-subjectivist approaches. Two broad approaches to justifying the laws of probability on subjectivist grounds are then discussed: (a) pragmatic approaches, based on betting behavior, with associated Dutch book arguments, or (more broadly) pragmatic approaches based on decision and preference theory, with its representation theorems; and (b) non-pragmatic (epistemic) approaches, with arguments based on calibration and gradational accuracy. These various arguments are assessed, and their scope and limitations spelled out in detail. Finally, the relation of subjective probability to the confirmation of scientific theories is discussed, focusing on the problem of old evidence, and its various proposed solutions.