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**Necessity, possibility, and contingency **are nothing but different MODES of truth. They function as operators on propositions, and they function strictly independently of notions like causation or ontological dependency.
And for purposes of philosophical discourse “contingent” does not mean “dependent on” in spite of what so many of you think. If you want to try to express the notion that some event, some thing, or some action is “dependent on” another event, thing, or action, then you need to use some phrase like “causally dependent,” “ontologically dependent,” or “metaphysically dependent.” When the rest of you say things like “God’s knowledge is logically contingent on John doing X” this doesn’t even make any sense! You merely mean to say that “God’s knowledge is caused by John doing X.” That would work much better so we can make sense of these notions.
More Wiki on Modal truth. And the article stands right in line with what I have been saying all along:
en.wikipedia.org/wiki/Modal_logic#Alethic_modalities
And for purposes of philosophical discourse “contingent” does not mean “dependent on” in spite of what so many of you think. If you want to try to express the notion that some event, some thing, or some action is “dependent on” another event, thing, or action, then you need to use some phrase like “causally dependent,” “ontologically dependent,” or “metaphysically dependent.” When the rest of you say things like “God’s knowledge is logically contingent on John doing X” this doesn’t even make any sense! You merely mean to say that “God’s knowledge is caused by John doing X.” That would work much better so we can make sense of these notions.
More Wiki on Modal truth. And the article stands right in line with what I have been saying all along:
en.wikipedia.org/wiki/Modal_logic#Alethic_modalities
In classical modal logic, a proposition is said to be
possible if and only if it is not necessarily false (regardless of whether it is actually true or actually false);
necessary if and only if it is not possibly false; and
contingent if and only if it is not necessarily false and not necessarily true (ie. possible but not necessarily true).
In classical modal logic, therefore, either the notion of possibility or necessity may be taken to be basic, where these other notions are defined in terms of it **[like contingency!]**in the manner of De Morgan duality.
The truth-makers, or ontology, of necessary, possible, and contingent truths:For those with difficulty with the concept of something being possible but not true, the meaning of these terms may be made more comprehensible by thinking of multiple “possible worlds” (in the sense of Leibniz) or “alternate universes”; something “necessary” is true in all possible worlds, something “possible” is true in at least one possible world. These “possible world semantics” are formalized with Kripke semantics.
In the most common interpretation of modal logic, one considers “logically possible worlds”. If a statement is true in all possible worlds, then it is a necessary truth. If a statement happens to be true in our world, but is not true in all possible worlds, then it is a contingent truth. A statement that is true in some possible world (not necessarily our own) is called a possible truth.
Whether this “possible worlds idiom” is the best way to interpret modal logic, and how literally this idiom can be taken, is a live issue for metaphysicians. The possible worlds idiom would translate the claim about Bigfoot as “There is some possible world in which Bigfoot exists”. To maintain that Bigfoot’s existence is possible, but not actual, one could say, “There is some possible world in which Bigfoot exists; but in the actual world, Bigfoot does not exist”. But it is unclear what it is that making this claim commits us to. Are we really alleging the existence of possible worlds, every bit as real as our actual world, just not actual? **Saul Kripke **believes that this is a misnomer – that the term ‘possible world’ is just a useful way of visualizing the concept of possibility.[5] For him, the sentences “you could have rolled a 4 instead of a 6” and “there is a possible world where you rolled a 4, but you rolled a 6 in the actual world” are not significantly different statements.[6] David Lewis, on the other hand, made himself notorious by biting the bullet, asserting that all merely possible worlds are as real as our own, and that what distinguishes our world as actual is simply that it is indeed our world – this world (see Indexicality).