What should and should not be considered an affordance is still an open issue. At the 2002 North American meeting of the International Society for Ecological Psychology, a symposium was held concerning this topic. The articles in this special issue are expanded versions of the papers presented at that symposium. To set the stage for those discussions, this article presents an analysis of the evolution of J. J. Gibson's thinking on this issue, from some of his earliest writings (i.e., J. J. Gibson & Crooks, 1938) through his most recent writings (i.e., J. J. Gibson, 1979/1986). It is hoped that this forum will stimulate thinking concerning this important ecological concept.