Topic: necessary truth

topics > philosophy > Group: meaning and truth

analytic truth
metaphysics and epistemology
names as rigid designators
number as a named set of numbers
what is truth


Modal logic concerns forms such as necessarily P and possibly P. Aristotle wrote about modal logic. Kripke is a modern proponent. He developed the idea of possible worlds that include the actual world that we live in. A fact is necessarily true if it is true in all possible worlds. It is possibly true if it is true in some possible world.

Necessity is tied with certainty, analyticity, Platonic forms, and scientific truth. It can get tricky and it's easy to use one to predefine the other.

Perhaps all that is necessary is number and names. Those are true by convention. Immensely useful, but not truth. (cbb 4/94)

Subtopic: necessary vs. contingent up

Quote: necessary and contingent propositions; what is (so) either is or is not (so) vs. something exists [»leibGW_1666]
Quote: possible truths are those that do not lead to contradiction; contingent truths lack resolution even if continued to infinity [»leibGW_1686]
Quote: absolute and hypothetical truths have the same laws; syllogisms are categorical

Subtopic: necessity up

Quote: a necessary fact is true in all possible worlds; e.g., if the Goldbach conjecture is true, it is necessarily true [»kripSA_1980]
Quote: the principles of eternal things are necessarily true; they explain the being of other things; e.g., fire is why things are hot [»aris_322a]
Note: list of modal forms--necessarily, possibly, not; behaves like forAll and thereExists; be careful of secondary occurrences [»kripSA_1980, OK]
Quote: 'Necessarily' and 'Possibly' are referentially opaque; depends on wording; e.g., "number of planets = 9" and "9 is necessarily greater than 7" [»quinWV_1947]
Quote: with strict modality, quantification does not make sense, nor does modal logic; necessity becomes a synonym for analytic [»quinWV_1947]
Quote: knowledge of an unconditioned necessity must itself be an unconditioned necessity and hence unknowable
Quote: necessary truths are those that reduce to identity; impossibles are those that lead to contradiction [»leibGW_1686]
Quote: the necessary reduces to an identity; the impossible reduces to a contradiction; the possible is not impossible
Quote: to argue, every word must indicate one definite thing, a necessary connection; opposite statements are impossible [»aris_322a]

Subtopic: analytic propositions up

Quote: if a language contains intension adverbs (necessarily) then interchanging equivalent predicates can demonstrate cognitive synonymy; analytic already [»quinWV1_1951]
Quote: analytical propositions are necessary because they record our determination to use words in a certain fashion [»ayerAJ_1956]
Quote: necessary truths and contingent truths differ as rationals differ from irrationals; the former reduces to identity while the later leads to infinite regress [»leibGW_1679]
Note: X and Y have the same sense when X and Y necessarily have the same reference in all possible situations [»fregG_1892, OK]

Subtopic: universal truth as numeric up

Quote: all truths can be explained by numbers [»leibGW_1686]
Quote: for every true universal, affirmative, categorical proposition the predicate is contained numerically in the subject [»leibGW4_1679]

Subtopic: contigent truth up

Quote: consider Neptune before it was ever seen; its description was an a priori truth but not a necessary one [»kripSA_1980]
Note: consider Nextperson as a proper name; its description fixes its reference but does not give its meaning; i.e., contingent, a priori truth [»kripSA_1980, OK]
Quote: for proper names, sense is necessary but reference is contingent; they look like shorthand or a vague description [»searJR_1958]

Subtopic: pure ideas up

Quote: scientific properties are necessary but not a priori, e.g., gold has atomic number 79, but was still gold beforehand [»kripSA_1980]
QuoteRef: russB_1912 ;;17 Plato: have pure ideas (e.g., justice and whiteness) of which reality is but a reflection.

Subtopic: necessity vs diversity up

Quote: blind necessity could produce no variety of things; diversity is due to the ideas and will of a Being necessarily existing [»newtI_1685, OK]
Quote: freewill must arise from something other than collisions of atoms; it is not bowed by necessity; nothing can emerge from nothingness

Related Topics up

Topic: analytic truth (51 items)
Topic: existence (29 items)
Topic: metaphysics and epistemology (99 items)
Topic: names as rigid designators (43 items)
Topic: number as a named set of numbers (15 items)
Topic: what is truth
(67 items)

Updated barberCB 7/05
Copyright © 2002-2008 by C. Bradford Barber. All rights reserved.
Thesa is a trademark of C. Bradford Barber.