 We will also steer clear of the philosophical debate over the exact nature of probability. The formal systems discussed here are compatible with all of the common interpretations of probability, but obviously, in concrete applications, certain interpretations of probability will fit more naturally than others. For example, the modal probability logics discussed in   Section 4  are, by themselves, neutral about the nature of probability, but when they are used to describe the behavior of a transition system, their probabilities are typically interpreted in an objective way, whereas modeling multi-agent scenarios is accompanied most naturally by a subjective interpretation of probabilities (as agents’ degrees of belief). This topic is covered in detail in Gillies (2000), Eagle (2010), and the entry on  interpretations of probability  of this encyclopedia.