This collection of essays originated from an interdisciplinary conference held at the University of Pittsburgh. Contents: Aesthetic Factors in Natural Science, by Nicholas Rescher; Three Arguments against Simplicity, by Kristin Shrader-Frechette; Simplicity and the Aesthetics of Explanation, by Joseph C. Pitt; Simplicity as an Epistemic Virtue: The View from the Neuronal Level, by Paul M. Churchland; Taming a Regulative Principle: From Kant to Schlick, by Matti Sintonen; Simplicity and Distinctness: The Limits of Referential Semantics, by Ulrich Majer; The Aesthetics of Theory Testing: Economy and Simplicity, by Jane Duran; Simplicity in Evolutionary Explanations, by David B. Resnik; and The Role of Simplicity in Geology, by illiam R. Brice. Index. Co-published with Center for the Philosophy of Science.