Hostname: page-component-7c8c6479df-995ml Total loading time: 0 Render date: 2024-03-29T05:26:47.376Z Has data issue: false hasContentIssue false

Peirce's axioms for propositional calculus

Published online by Cambridge University Press:  12 March 2014

A. N. Prior*
Affiliation:
Canterbury University College, Christchurch, New Zealand

Extract

In 1885 Peirce axiomatised the propositional calculus on the basis of five ‘icons’ or axioms, which with Cpq for ‘If p then q’ and o for a false proposition, and with the source in Peirce's [2] beside each, may be represented as follows: 1. Cpp (3.376); 2. CCpCqrCqCpr (3.377); 3. CCpqCCqrCpr (3.379); 4. Cop (3.381); 5. CCCpqpp (3.384). From these Peirce proves, among other things, 6. CpCCpqq (3.377), 7. CpCqp (3.378), and with Np (Not p) for Cpo, 8. CNNpp (3.384).

By a well-known result of Wajsberg's II. 93, the entire two-valued propositional calculus is derivable by substitution and detachment from 3, 4, 5, and 7 (with Df. N). In Berry [1] this is taken to show the completeness of Peirce's basis; but this proof will not do as it stands. For Peirce's proof of 7 consists in first passing from 1 to CqCpp by the argument that ‘to say that (xx) is generally true is to say that it is so in every state of things, say in that in which y is true’; and then from CqCpp to 7 by 2. This procedure clearly involves, formally, the use not only of substitution and detachment but of a rule to infer ⊦ Cqα. from ⊦α. Peirce's basis is sufficient with substitution and detachment nevertheless; for by a less well-known result of Wajsberg's II. 93, 3, 4, 5, and 6 are sufficient in this sense, and Peirce does prove 6 by substitution and detachment from 1 and 2.

Type
Research Article
Copyright
Copyright © Association for Symbolic Logic 1958

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

[1]Berry, George D. W., Peirce's contributions to the logic of statements and quantifiers, in Studies in the philosophy of Charles Sanders Peirce, ed. Wiener, Philip P. and Young, Frederic H. (1952).Google Scholar
[2]The collected papers of Charles Sanders Peirce, edited by Hartshorne, Charles and Weiss, Paul; Harvard University Press, Cambridge (19311935).Google Scholar