In this article I discuss the justification of scientific change and argue that it rests on different sorts of invariance. Against this background I consider notions of observation, meaning, and regulative standards. I sketch an account of the rationale of scientific change which preserves the merits and avoids the shortcomings of the approach of Feyerabend, Hanson, Kuhn, Toulmin, and others. Each of these writers would hold that transitions from one scientific tradition to another force radical changes in what is observed, (...) in the meanings of the terms employed, and in the metastandards involved. They would claim that "incommensurable" replacement is what does, and should, occur during scientific "revolutions." Such writers, however, have trouble in comparing different scientific theories. My account permits different theories to be compared in various ways. These comparisons, I argue, are possible through appeal to "first-level" and "second-level" invariance. In this connection I argue that observation, meaning, and regulative standards should be, and in fact usually are, nontrivially invariant with respect to scientific change. (shrink)

Feyerabend claims that what is perceived depends upon what is believed ; and he maintains that among really efficient alternative theories "each theory will possess its own experience, and there will be no overlap between these experiences". According to Feyerabend "scientific theories are ways of looking at the world; and their adoption affects our general beliefs and expectations, and thereby also our experiences...". Toulmin, Hanson, and Kuhn concur with this view. Toulmin claims that men who accept different "ideals" and "paradigms" (...) will see different phenomena. He thinks theories not only give significance to facts, but also determine what facts are for us at all. Like Feyerabend, Toulmin asserts that "we see the world through" our fundamental concepts of science "to such an extent that we forget what it would look like without them". Indeed, both Feyerabend and Toulmin would have previous thinkers "live in an observational world very different from our own". Kuhn expresses quite similar views. He feels that. (shrink)