Validity Conditions and Unanalysed Propositions

Alexander Broadie

in Introduction to Medieval Logic

Second edition

Published in print April 1993 | ISBN: 9780198240266
Published online October 2011 | e-ISBN: 9780191680137 | DOI:
Validity Conditions and Unanalysed Propositions

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In the earlier phases of medieval logic, the theory of inference was treated as a theory applying specifically to propositions in so far as those propositions displayed the form of categoricals. Rules of valid inference designed to deal with the inferential power of propositions which are specifically categorical are rules for analysed propositions. However, there are also rules of inference which, though applicable to categorical propositions, are applicable independently of the internal structure of those propositions. Instead they apply to categorical propositions merely as propositions, and they apply to molecular propositions merely as molecular. For such rules it is the propositional connectives and the sign of negation that are important, and the quantifiers are of no importance whatever. Rules of the latter kind are rules for what are termed unanalysed propositions. This chapter discusses the rules of valid inference for unanalysed propositions and examines double negation, some basic rules of inference, and modus ponens and modus tollens.

Keywords: valid inference; unanalysed propositions; double negation; modus ponens; modus tollens; medieval logic; categorical propositions

Chapter.  9353 words. 

Subjects: Philosophy of Mathematics and Logic

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