The Modern Epistemic Interpretations of Probability: Logicism and Subjectivism

The chapter focuses on the modern epistemic interpretations of probability, namely logicism and subjectivism. The qualification “modern” is meant to oppose the “classical” interpretation of probability developed by Pierre Simon de Laplace (1749-1827). With respect to Laplace’s definition, modern epistemic interpretations do not retain the strict linkage with the doctrine of determinism. Moreover, Laplace’s “Principle of insufficient reason” by which equal probability is assigned to all possible outcomes of a given experiment (uniform prior distribution) has been called into question by modern epistemic interpretations and gradually superseded by other criteria. The main traits of the logical and subjective interpretations of probability are outlined together with the position of a number of authors who developed different versions of such viewpoints.