Psychology Dictionary of ArgumentsHome
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| Modal logic: the modal logic is an extension of classical logic to systems in which possibility and necessity can also be expressed. Different approaches use operators to express "necessary" and "possible", which, depending on the placement within formulas, can let claims of different strengths win. E.g. there is an object which necessarily has the property F/it is necessary that there is an object with the property F. The introduction of possible worlds makes quantification possible for expressing possibility (There is at least one world in which ...) and necessity (For all worlds is valid ...). See also operators, quantifier, completion, range, possible worlds._____________Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments. | |||
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Peter Geach on Modal Logic - Dictionary of Arguments
I 174f Necessary/necessity/modal/Geach: it is even necessary necessary, that no one who is a brother is not male. Because if it were necessary only contingently, it would still be a possible option to be a brother that is not a male, even if no real opportunity! (> NNa, MMa) - if Descartes had said that necessarily God would have to create the necessity that a brother is male he would have talked big nonsense. >Necessity, >Necessity de re, >de re, >de dicto, >Systems S4/S5._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. Translations: Dictionary of Arguments The note [Concept/Author], [Author1]Vs[Author2] or [Author]Vs[term] resp. "problem:"/"solution:", "old:"/"new:" and "thesis:" is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition. |
Gea I P.T. Geach Logic Matters Oxford 1972 |
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> Counter arguments against Geach
> Counter arguments in relation to Modal Logic
