Behavioral and Brain Sciences

Short Communication

Visual imagery and geometric enthymeme: The example of Euclid I.1

Keith K. Niall a1
a1 Defence and Civil Institute of Environmental Medicine, Defence Research & Development Canada, Toronto, M3M 3B9, Canada [email protected]


Students of geometry do not prove Euclid's first theorem by examining an accompanying diagram, or by visualizing the construction of a figure. The original proof of Euclid's first theorem is incomplete, and this gap in logic is undetected by visual imagination. While cognition involves truth values, vision does not: the notions of inference and proof are foreign to vision.