High Quality Content by WIKIPEDIA articles! The propensity theory of probability is one interpretation of the concept of probability. Theorists who adopt this interpretation think of probability as a physical propensity, or disposition, or tendency of a given type of physical situation to yield an outcome of a certain kind, or to yield a long run relative frequency of such an outcome. This kind of objective probability is sometimes called 'chance'. Propensities, or chances, are not relative frequencies, but purported causes of the observed stable relative frequencies.