GOD AND COSMOS (2)
N OT every version of the Cosmological Argument turns on the notions of cause and effect. St Thomas's Third Way -- the argument about 'might-not-have-beens' -- uses instead the concepts of 'contingency' and 'necessity'. The contingent is what happens to exist, but need not have existed: necessary being is being that has to exist, that cannot not exist. The argument states that if there are contingent beings, there must be a necessary being. The one is correlative to the other, like 'front' and 'back', 'up' and 'down', 'convex' and 'concave'. The fact of a contingent world implies the fact of a necessary being whose world it is, and whose permanence stands behind the world's mutability.
The first difficulty about this version arises from the fact that 'necessary' and 'contingent', when used as correlatives, are words normally at home in speaking not of things or beings, but of propositions; a 'necessary' proposition being one that cannot be denied without contradition, whereas a contingent one can. If we wish to keep this logical use of 'necessary' and 'contingent', we could rephrase the Argument in this way: 'The proposition "God exists" is necessary.' That is, it would be contradictory to deny God's existence. But Hume very properly objected to this that one may deny the existence of any thing or person whatever and never involve oneself in logical contradiction, although sometimes, of course, in falsity. To get a contradiction in such a