"Rather than treating the content of a natural science as a tight and coherent logical system, we shall... have to consider it as a conceptual aggregate, or 'population', within which there are—at most—localized pockets of logical systematicity. Seen in this light, the problem of scientific rationality can be restated in new terms. ...The extreme 'revolutionary' view of conceptual change remains attractive... only if we make the twin mistakes of equating 'rationality' and 'logicality', and supposing that an entire science has the same logical coherence as (say) Euclid's geometry of Newton's mechanics. ...Those who assume that an entire science necessarily forms a single, coherent intellectual system will correctly infer that 'radical' changes in its intellectual content must also be 'revolutionary'. In this respect, the problems arising over Kuhn's account of scientific change have significant parallels in sociology and elsewhere. The belief that society as a whole forms a single coherent and functional 'social system'... is a direct counterpart to the belief that physics as a whole forms a coherent 'logical system'. An oversytematic analysis of social structure has, in fact, dominated a great part of sociological theory for almost as long as its logical counterpart has dominated the philosophy of science; and, in each case, the revolutionary view is an understandable over-reaction to that domination. ...We can view an entire society as forming a single functional 'system', only if we fail to distinguish the looser social and political relations between the different institutions of a society ...[A]n entire science comprises an 'historical population' of logically independent concepts and theories, each with its own separate history, structure, and implications."