Journal of Logic and Computation Advance Access published online on April 22, 2008
Journal of Logic and Computation, doi:10.1093/logcom/exn001
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Original Papers |
Pedagogical Second-order Propositional Calculi
University of Metz, Metz, France E-mail: colson{at}univ-metz.fr; david.michel{at}univ-metz.fr
Received 18 June 2007.
| Abstract |
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The present work introduces the notion of pedagogical natural deduction systems, which are natural deduction systems with the following additional constraint: all hypotheses made in a proof must be motivated by an example. Technically speaking, we replace the rule (Hyp):
with the rule (PHyp):
with
denoting a substitution replacing all variables of
with an example. This substitution is called the motivation of
. These systems are in essence negationless. In the present article, we study the second-order propositional calculus, since it is the simplest non-trivial natural deduction system in which the negation is definable. Some pedagogical versions of the second-order propositional calculus are proposed. We argue that these pedagogical calculi are negationless and we study their expressive power.
Keywords: Constructive mathematics; mathematical logic; natural deduction; negationless mathematics; typed
-calculus