Science educators and those who investigate science learning have tended, for good reason, to focus their attention on students' conceptual development, Such a focus is, however, too narrow to provide full and proper understanding of the complexities of original science learning. Recently developmental cognitive psychologists have called on the work of postpositivistic philosophers of science, especially Thomas Kuhn, to bolster their research into conceptual development in science acquisition. What these psychologists have not recognized is that Kuhn's position is actually a (...) derivative of Wittgenstein's methodological nominalism, a viewpoint far more favorable to behaviorism than cognitive psychology. After drawing out some of the consequences of this fact for the developmental cognitive psychologist program for studying science learning, we suggest our own radical alternative. Drawing on Floden, Buchmann and Schwille's idea of “Breaking with Everyday Experience” we propose an alternative notion of original science learning in terms of Alfred Schutz's modification of Williams James' many worlds thesis. The many worlds thesis will allow us to better understand students' difficulty in learning idealized worlds such as science, worlds that represent a discontinuous break with ordinary everyday practical experience. (shrink)