This paper presents a cognitive analysis of subjective probability judgments and proposes that these are assessments of belief-processing activities. The analysis is motivated by an investigation of the concepts of belief, knowledge, and uncertainty. Judgment and reasoning are differentiated, Toulmin's (1958) theory of argument being used to explicate the latter. The paper discusses a belief-processing model in which reasoning is used to translate data into conclusions, while judgmental processes qualify those conclusions with degrees of belief. The model sheds light on traditional interpretations of probability and suggests that different characteristics of belief--likelihood and support--are addressed by different representational systems. In concluding, the paper identifies new lines of research implied by its analysis.