An examination of earlier views yields an account of theoretic change on which changes in theory which do involve changes in meanings of terms are classified as a special (and by no means exhaustive) case of theoretic change which, latter, is construed as a more general phenomenon. Only the general problem is given detailed consideration here. The account given considers the problem of how replacement of intensional theories by extensional ones may be treated within the general framework provided. Among its (...) results is the conclusion that rational changes in a scientific theory may be cogently construed as determined by warranted decisions that a new theory is more adequate (than the old one it replaces) with regard to purposes for which a theory is sought. (shrink)