This article deals with the social meaning of insurance contracts in the late medieval and modern society. Starting from the empirical analysis of one of the early marine insurance contracts which were stipulated in the second half of the 14th century, the hypothesis is suggested that the premium rate coincides with the estimated average frequency of sea accidents. By means of a proto‐probability calculus, rate was used by the early insurers for trading risks. Therefore the main thesis arises that insurance premium is a way of giving a certain price to the uncertainty of the future and that it indeed represents the cost of such observation. A comparison with the original function of money in primitive societies based on reciprocity is finally developed in order to explain how time construction is contingent on social structures.