Abstract

Modal concepts - among them the concepts of logical, physical (nomic) and metaphysical necessity - used to be quite important for philosophy of science during centuries. However, in the XX c. most philosophers preferred not to recognize those concepts in science (especially the concept of physical necessity). They were wrong. Some patterns from history of physics are presented, showing the concept of physical necessity playing an important role in the scientific research of nature. And the nature of physically necessary statements is different from both logically necessary statements - on the one hand - and contingent statements, on the other. Consequently three attempts to explain the nature of physical necessity are discussed. (1) Physical necessities are just relative necessities, logical consequences of physical laws. (2) Logical and physical necessities are of the same nature, although logically necessary statements are as well analytical, while those physically necessary are synthetic. Some serious difficulties arising in both theories are shown. Finally a third explanation is outlined. (3) The two kinds of necessary statements differ in their reference: they describe different kinds of real relationships (connection)