Fiat and Bona Fide Boundaries

Barry Smith

Department of Philosophy and Center for Cognitive Science

State University of New York at Buffalo, Buffalo, NY

Achille C. Varzi

Department of Philosophy
Columbia University, New York, NY

Philosophy and Phenomenological Research, 60: 2, March 2000, 401–420. 


We argue that the basic typology of spatial boundaries involves an opposition between bona fide (or physical) boundaries on the one hand, and fiat boundaries on the other, the latter being exemplified especially by boundaries induced through human demarcation, for example in the geographic realm. The classical metaphysical problems connected with the notions of adjacency, contact, separation and division can be resolved in an intuitive way by recognizing this two-sorted ontology of boundaries. Bona fide boundaries yield a notion of contact that is effectively modeled by classical topology; the analogue of contact involving fiat boundaries calls, however, for a different account, based on the intuition that fiat boundaries do not support the open/closed distinction on which classical topology is based. In the presence of this two-sorted ontology it then transpires that mereotopology—topology erected on a mereological basis—is more than a trivial formal variant of classical point-set topology.

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