Published online by Cambridge University Press: 28 February 2022
Natural sciences such as geology, geography, and astronomy are mainly interested in describing features of the real world. Other sciences such as physics and chemistry deal with certain classes of possible phenomena, no matter whether they really taken place or not. The former sciences are based on the latter, so that all are interested in possible phenomena or worlds.
Roughly speaking, on the one hand there are some axiomatic theories - e.g. theories of classical mechanics similar to Newton's presentation of mechanics - that speak of phenomena occurring in the typical possible world, without considering basic relations involving several of these worlds. These theories do not aim very much at reducing primitive concepts. On the other hand, to make assertions involving possible worlds is practically compulsory in theories that include the definition of some constitutive magnitudes, i.e. magnitudes that characterize the reaction of a system S to a situation Σ possibly depending on parameters.
This conference was prepared in the sphere of activity of the research group for mathematical physics of the Consiglio Nazionale delle Ricerche, in 1971-72 and 1972-73.