"This is an exciting epistemological experiment. It is wonderful to see how intelligent philosophers can take a modest concept, such as that of the bole, as a starting point for an immense and brilliant exercise.... The writing is delightful."
- Valentino Braitenberg, Director, Max-Planck Institut Für Biologische Kybernetick

This fascinating investigation on the borderlines of metaphysics, everyday geometry, and the theory of perception seeks to answer two basic questions: Do holes really exist? And if so, what are they?

Holes are among entities that down-to-earth philosophers would like to expel from their ontological inventory. Casati and Varzi argue in favor of their existence and explore the consequences of this unorthodox approach - odd as these might appear. They examine the ontology of holes, their geometry, their part-whole relations, their identity, their causal role, and the ways we perceive them.

Three basic kinds of holes are distinguished: blind hollows, perforating tunnels, and internal cavities. Treating these uniformly as immaterial bodies, Casati and Varzi develop a morphology of holes, focusing on how a hole can be filled. They then look at the main properties of the resulting conceptual framework: Holes, they observe, are parasitic upon the surface of their hosts; holes can move, fuse into one another, split; they can be born, develop, and die. Finally, the authors examine how some morphological features of holes are represented in perception, including the conditions whereby we have the impression that we see, feel, or even hear a hole.

Roberto Casati is Assistant in the Department of Philosophy at the University of Neuchatel, in Switzerland. Achille C. Varzi is with the Istituto per la Ricerca Scientifica e Tecnologica in Trento, Italy.