An examination of the introspective evidence of artists and scientists on their creative processes suggests that determining the causes underlying the transformation of material in thought is the key for understanding creativity. A similar problem underlies the transformational process of understanding metaphor. T.S. Kuhn's view of scientific revolutions and the nature of thought in dreams provides evidence for transformations in thought under the impact of experiential anomalies. Such transformations are guided by or express affective states or attitudes. Evidence for the productive role of affect in thought can be found in several sources, including research on the frontal regions of the brain and the affective correlates of response to metaphor. An adequate theory of creativity must await further research on the anticipatory properties of affect, but a useful place to begin research is with the response to metaphor. (Author/FL)