Thursday, 15 September 2016

Metaphysical Necessity

Yesterday, I asked whether it is a strict logical possibility that William Lane Craig is a lying doofus.  Today, I want to ask whether it is a metaphysical necessity that William Lane Craig is a lying doofus.

Some may be sad to learn that I think that the answer is a resounding "No", but please stay with me as I try to explain how I reach this conclusion.

When reading the Wikipedia page on "metaphysicalnecessity", we immediately come across words that are faintly familiar:

In philosophy, metaphysical necessity, sometimes called broad logical necessity, is one of many different kinds of necessity, which sits between logical necessity and nomological (or physical) necessity.

Compare this with the words of WLC:

… The answer is “metaphysical possibility.”  This is a modality in between physical possibility and strict logical possibility and is often called “broad logical possibility” by contemporary philosophers.

So, it would appear that WLC took the notion of "broad logical necessity" (likely coined by Plantinga in The Nature of Necessity in 1974), twisted it into a new form, that being "broad logical possibility", and claimed that contemporary philosophers were already talking about it.  I saw the term "metaphysical necessity" in one of the very early documents that refer to "broad logical possibility", the transcript of a talk by … yep, William Lane Craig (The Coherence of Theism).

In this document, you can see evidence of the switch from "broad logical necessity" to the new term "broad logical possibility":

Furthermore, the modality operative in possible worlds semantics is not strict logical necessity/possibility, but broad logical necessity/possibility. Strictly speaking there is no logical impossibility in the proposition The Prime Minister is a prime number; but we should not want to say, therefore, that there is a possible world in which this proposition is true.

It is true that people have been talking about metaphysical necessity for a very long time, but what exactly do we mean by "people" here?  Most of these people have been theists talking about god, or talking about Saul Kripke (who in turn was talking about what was referred to in Strict Logical Possibility as "metaphysical possibility").  Again, when we try to consider things that fall into this category, now considered in terms of necessity, rather than possibility, we can find only one thing that is claimed to be "metaphysically necessary" - and that is a god, most specifically the god of the ontological argument.  There's a neat little Venn diagram on this page that sums things up nicely.

Let us put Kripke's modal logic tautologies aside (ie put aside notions similar to it being "metaphysically necessary" that water is H2O and vice versa (at which point we need to also put aside the confusion of people who don't accept that ice is also water, despite it having a different name and being a lattice rather than liquid form)).  Other than a god, what does anyone claim to be a "metaphysical necessity"?

When I first started developing the idea for what became Strict Logical Possibility, I was very much thinking about the awkward negation of "strict logical possibility".  People tend to get confused about how modals are negated and casual modern English (particularly as used by Americans) only makes the confusion worse.

For example, if I were to say that "not all" cats are grey, I am not suggesting direct opposite of "all cats are grey" - that is I am not say that all cats are not grey.  If I wanted to say that, I would say "no" cats are grey (or all cats are "not grey".  In clumsy usage, "all cats are not grey" is often meant to say "some cats are grey, but not all of them" - rather than "every single cat that exists is some colour other than grey".  (I'm somewhat ambivalent on the grey/gray divide, although I do see Gray as more of a surname than a colour.)

This confusion carries over to considerations of what is possible/necessary and not possible/necessary (see Plantinga and His BS5).  In brief that which is not possible cannot be necessary, but that which is not necessary can be possible.  In other words, a lack of necessity is consistent with both possibility and impossibility.  WLC does not fall into the trap of saying explicitly that the non-existence of god is metaphysically impossible, but others certainly do:

William L. Rowe has challenged my claim that there are only two kinds of impossibility, logical and physical, by introducing the concept of metaphysical impossibility — the impossibility which obtains just in case nothing has the power to bring about an individual’s non-existence — and by maintaining that, though God’s non-existence is metaphysically impossible, it does not follow that it is logically impossible as well.

And the ontological argument is based very much on the notion that the non-existence of the god in question is metaphysically impossible - which is to claim that the existence of god is metaphysically necessary.  WLC certainly makes the claim that the existence of his god is ametaphysical necessity:

(blah blah blah, blah blah) … Thus, it is metaphysically necessary that God exists.

But now we are back to the question of what things are metaphysically necessary - if there is nothing else than god in this category (and possibly all those tautological claims that things are the things that they are), then surely the claim that god is "metaphysically necessary" has no teeth whatsoever.  God would have the precisely the sort of "metaphysically necessary" existence that god has (which could easily be no existence whatsoever) and god would have the precisely the same characteristics that god has (being spaceless, timeless, immaterial and non-existent).

WLC goes on in the article linked above to write:

We have here the germ of the ontological argument for God's existence. For if it is possible that God exists, there is a possible world in which God has necessary existence. But then He exists in every world, including this one. Thus, the atheist is thrust into the awkward position of having to say that God's existence is impossible. It is not enough to say that in fact God does not exist; the atheist must hold that it is impossible that God exists—a much more radical claim!

He's claiming here that, because the atheist disagrees with the claim that the existence of god is a (metaphysical) necessity, she needs to hold that existence of god is a (metaphysical) impossibility - perhaps even to the extent that the non-existence of god is a metaphysical necessity.  This is a false dilemma built on a(n implied) begged question - buried in the fact that the only object that is asserted to have a metaphysically necessary existence is a god.  The atheist is quite entitled to allow that gods are a metaphysical possibility, whatever is actually meant by that, while holding that none actually exist (for reasons other than metaphysical necessity/possibility).

Finally, I did say that I did not want to claim that is a metaphysical necessity that WLC is a lying doofus.  I think it's quite reasonable to be averse to putting the assertion "god exists" on a par with "WLC is a lying doofus".  After all, I am quite convinced that god does not exist.

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