Abstract

It would appear that among scientific men discussion of the general principles of natural science has, on the whole, proved more congenial to mathematicians and physicists than to biologists. Just why this should be so might be difficult to explain or justify. But one reason seems to lie in the comparative ambiguity of the concept of causation in biology. In general, the term causation has been used in science to designate the special rôle of active factors, rather than of passive or stable factors, in the determination of single events. By active factors we mean those which involve physical change, typically associated with transfer of energy; these are distinguished from stable factors or invariants which persist unchanged throughout the process under consideration. Thus in the classical isolated system, the total energy represents a stable factor which remains the same through all transformations of the system. The energy changes its form, potential or distribution, but not its total quantity. This rule of conservation defines a static condition persisting as a limiting factor through any case of change. Similarly, the permanent or unchanging factor in a machine consists in the stable properties and structural interconnections of its parts; together those constitute an invariant which fixes definitely the possible range of activity. Activity itself requires flow of energy; strictly speaking, a causal factor is not a static factor but is a change of some kind; releasing events are included under causal events since they introduce factors without which change does not occur.