Quote:
Originally Posted by John21
By way of the big IF. It’s possible the person x was never born (no-x); it’s possible his parents named him Robert (a ≠ x); it’s possible he chose a different pen name (b ≠ x); etc. So in any of those possible worlds, a ≠ b necessarily.
1) IF God exists, then God exists necessarily.
2) God exists.
3) Therefore, God exists necessarily.
4) IF Samuel Clemens is Mark Twain, then Samuel Clemens is Mark Twain necessarily (law of identity).
5) Samuel Clemens is Mark Twain.
6) Therefore, Samuel Clemens is Mark Twain necessarily.
In both arguments, (1) and (4) make a hypothetical claim about what is sufficient for a necessary claim to be true. In both arguments (2) and (5) claim this antecedent has been met, thus showing that (3) and (6) are true. However, (5) is an empirical claim about the world, subject to the same probabilistic rules of evidence as other empirical claims about the world. We do not learn that Samuel Clemens is Mark Twain through pure reason, but through an investigation of the world, an investigation that is inherently uncertain.
You have claimed that if we accept (1), we can only accept (2) if we also accept (3). I agree. However, that does
not imply as you are assuming that therefore (2) must be a non-empirical claim. (2), just like (5), can still be an empirical claim subject to the ordinary rules of evidence we use for other empirical claims, even if its truth implies some other claim is necessarily true.
Also, you are a bit confused here. It doesn't matter if Samuel Clemens's mother had given him a different name. (5) is
not saying that the name "Samuel Clemens" is identical to the name "Mark Twain." That is obviously false. Rather, it is saying that the
person referred to as "Mark Twain" is the same as the
person that is referred to as "Samuel Clemens." If truth, that is true regardless of what names we use to refer to him.