It has been traditionally assumed that, even if metaphors assist us in appreciating certain features of perceived objects and events, they play no epistemological role in the way we come to understand the world. This claim is challenged, and the challenge is substantiated by a survey of three philosophers who evidently believed that they were laying down epistemological foundations. In the case of Locke, Condillac and Kant, the ubiquity of the figurative language of rhetoric is acknowledged, and an attempt is made to diminish its importance for knowledge. In spite of the efforts of these thinkers, it turns out to be impossible to isolate rhetoric from language with fixed meanings and to banish the former to aesthetics, where meanings are supposed to be ambiguous. It is futile to seek to eliminate the rhetorical structure of texts in favor of some more "objective" structure. At this point aesthetic and epistemological distinctions collapse, and metaphor can be seen as operating creatively in the shaping and extending of our understanding. (Mark Johnson)