James W. McAllister is university lecturer in the Faculty of Philosophy at the University of Leiden. He received his Ph.D. from the University of Cambridge in 1989. He is the author of Beauty and Revolution in Science, published by Cornell University Press, 1996, on which this article is based. Address: Faculty of Philosophy, University of Leiden, P.O. Box 9515, 2300 RA Leiden, The Netherlands. Internet: mcallister@rullet.leidenuniv.nl