A TECHNIQUE FOR DETERMINING CLOSURE IN SEMANTIC TABLEAUX by Steven J. Bartlett Visiting Scholar in Philosophy and Psychology, Willamette University and Senior Research Professor, Oregon State University Website: http://www.willamette.edu/~sbartlet KEYWORDS: semantic tableaux, rules of closure, counterexample constructions, proof theory This paper was originally published in the Netherlands, in Methodology and Science: Interdisciplinary Journal for the Empirical Study of the Foundations of Science and Their Methodology, Vol. 16, No. 1, 1983, pp. 1-16. Methodology and Science ceased publication in the mid-1990s and all rights to this paper reverted to the author. This electronic version supplements the original text with internet-searchable keywords. The author has chosen to re-issue this work as a free open access publication under the terms of the Creative Commons Attribution-NonCommercialNoDerivs license, which allows anyone to distribute this work without changes to its content, provided that both the author and the original URL from which this work was obtained are mentioned, that the contents of this work are not used for commercial purposes or profit, and that this work will not be used without the author's or his executor's permission in derivative works (i.e., you may not alter, transform, or build upon this work without such permission). The full legal statement of this license may be found at http://creativecommons.org/licenses/by-nc-nd/3.0/legalcode © Steven James Bartlett,