User:MPeterHenry/Language of logic

It is essential to distinguish logic as language from logic as deduction or calculus.^[1], but already present from the beginnings of logic. In Aristotle's work,besides the celebrated study of the diffeerent kinds of syllogisms, there is an elucidation of the structure of propositions. Much later, Frege who began the revival of Leibniz's project, assigns to his Begriffsschrift an aim, that is not merely formalization for checking the correctness of arguments or reasonings, but also to express adequately (not as natural language does) the various thoughts. He claims that, unlike Boole's, his logic is not not merely a calculus ratiocinator, but a lingua characterica in Leibniz's sense.

When the language of first-order predicate logic and its extensions is treated this way as a foreign language, formalisation, interpretation or representation of English sentences are simply translations in this new language.

This can be done on an intuitive basis, as for any other languages, or in an automatic way, as in Montague or Kamp's discourse representation theory.

Vocabulary

Non-logical vocabulary

propositional symbols, predicate and function symbols, of given arity.

Logical vocabulary

variables (free and bound);
logical constants (including quantifiers, tense, modal, deontic, relevant operators, etc.);
punctuation marks, like parentheses, brackets, dots...

Syntax

Terms are build up with function symbols and variables;

Atomic formulae are build up with terms and predicate symbols;

Formulae are build up with atomic symbols and logical constants.

Sentences are formulae without free variables.

Examples

Universe of discourse: human beings. $L$ binary predicate symbol meaning ...loves....

$\forall x\exists yLxy$ = Everyone loves someone.

$\exists y\forall xLxy$ = Somebody is loved by everyone.

$\forall x\exists yLyx$ = Everyone is the beloved of someone.

$\exists y\forall xLyx$ = Somebody loves everyone.

References

^ This distinction was stressed by Van Heijenoort"Logic as Language and Logic as Calculus," Synthese, volume 17: pages 324-30.

External links

Translation Tips
"Discourse Representation", Bart Geurts and David I. Beaver, Stanford Encyclopedia of Philosophy
"Logical Form", Paul Pietroski, Stanford Encyclopedia of Philosophy

[1] This distinction was stressed by Van Heijenoort"Logic as Language and Logic as Calculus," Synthese, volume 17: pages 324-30.

[1]