Term used by the mathematician Richard von Mises (1883–1953) in Probability, Statistics, and Truth (1957; 1st German edn, 1928) for a sequence of events constituting a ‘mass phenomenon’ or sufficiently large repetition of an underlying cause, to form the basis for an attribution of probability. A large number of tosses of an identical coin, or large number of persons taking a certain drug, or large number of molecules in a gas in a certain state, may afford the basis for a probability judgement: that heads is 0.5 probable, that the chance of a heart attack is 0.1, or that the chance of a collision with another molecule in a certain time has a certain value. Treated mathematically a collective may be regarded as an infinite sequence of events, on each of which the chance of some attribute occurring is identical. The mathematical collective is an idealization of empirically given collectives, which have only finite numbers of members. See also frequency theory of probability.