This book presents a novel theory of probability and judgements of probability: strong coherentist subjectivism. James Logue combines three claims in his exposition of this theory. The first states that probabilities may be treated as the degrees of partial belief of (ideally rational) agents, best-established by the examination of behaviour. Thus, probability is personalist. The second claim contends that only such degrees of belief can be construed as probabilities: on this strongly subjectivist view the notion of objective chance is, if not conceptually impossible, at any rate redundant. The third, coherentist, claim maintains that minimal coherence of probability-beliefs is all that is necessary for those beliefs to be rational; on this view, weak coherence of a set of beliefs is both a necessary and sufficient condition for the rationality of those beliefs.