Is it a strict logical possibility that William Lane Craig is a lying doofus?
While this might seem like a totally uncalled for attack on WLC's person, it is merely meant as an example of how we might think about "strict logical possibility".
First we need to define our terms. When we look up "strict logical necessity" we might be disturbed to note that there are only 35 hits (excluding the hits that result from this post). The vast majority of them (including this post) make reference to WLC or Plantinga.
This led me to believe that "strict logical possibility" is another taxi-cab, a vaguely impressive sounding piece of nonsense created by William Lane Craig. A bit more manipulation of Google reveals that the phrase might actually have been a William Dembski original from a 2003 document on the flagellum, a phrase that was then resurrected by WLC in 2007. Dr Glen Martin used the words in that order in 2004, but the use doesn't appear to be intended as a phrase. I'm not entirely certain that Demski meant it to be a specific phrase either, since he also used "strict logical certainty", "strict logical deduction" and "strict identity" in the same document - so I think we would not be far off the mark if we were to award authorship of this nonsense to WLC. I was inclined to be generous. However, I found that there was an earlier clear use of the term, in 2006, by Sean Michael Campbell (nestled in a reference to "strict and broad logical possibility") - but this was in an overview of WLC's Kalam argument and, in the footnotes, Campbell acknowledges helpful conversations with WLC.
Since WLC was likely the person ultimately responsible for the coining of the phrase, we can look to him to see what it means. WLC first uses the term in "Causal Premiss (sic) of the Kalam Argument":
Your first question is, “What is the sense of ‘possibility’ here?” 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. To illustrate, it is strictly logically possible that “The Prime Minister is a prime number” (there is no logical contradiction here); but, notwithstanding, such a thing is metaphysically impossible (incapable of actualization). There are all sorts of truths—like “Everything that has a shape has a size,” “Nothing can be red all over and green all over,” “No event precedes itself,” etc.—which are not strictly logically necessary but are, I think, metaphysically necessary. I think that the first premiss of the kalam argument is a metaphysically necessary truth.
I note that "broad logical possibility" was not a term used often by "contemporary philosophers". It was a term used once, by one guy, after chatting with WLC. Making such a statement is what contemporary philosophers refer to as "a lie".
Sadly, WLC doesn’t really define "strict logical possibility". Although he does hint that something has "strict logical possibility" when it doesn't entail a logical contradiction, it isn't clear whether this is key to defining the term or merely a feature of things that have "strict logical possibility". Fortunately, we have a later reference to the phrase to work from, a quite recent one - In what sense is it impossible for the universe to come from nothing? - 11 September 2016.
When the atheist professor says that “it may be possible that something began to exist out of nothing because that statement did not involve a contradiction,” he is talking about strict logical possibility. He’s quite right that “The universe began to exist out of nothing” involves no logical contradiction and is therefore strictly logically possible. Where he errs is thinking that this is of any philosophical significance.
So, "strict logical possibility" equals "not entailing a contradiction". This is a construction that is bound to end in tears, since it's hiding a negation in a phrase with two adjectives and a noun - a noun that is conjugated from yet another adjective (ie possible). And WLC just leaps right in to discuss the impossible, negation of the possible. He's canny though, since he doesn't talk about "strict logical impossibility" - he merely talks about "broad logical impossibility" (and "metaphysical impossibility", more on that in a moment).
WLC makes clear that "strict and broad logical possibility" (the original phrasing from Campbell) are distinct, meaning that "strict logical possibility" is distinct from "broad logical possibility" and "broad logical possibility" is distinct from "strict logical possibility". Therefore, we are led to conclude, something that has "broad logical possibility", since it is not "strict logical possibility" can entail a (logical) contradiction. Read the paragraph above again. WLC wrote "(X) involves no logical contradiction and is therefore strictly logically possible".
Bizarrely, WLC then writes:
It’s also strictly logically possible that “John is a married bachelor” or that “The Prime Minister is a prime number.” So what? That goes no distance toward showing that married bachelors are metaphysically possible or that it is metaphysically possible that the Prime Minister is a prime number. What we want to know is whether such states of affairs are realizable or actualizable. Could John really be a married bachelor or the Prime Minister a prime (or any other sort of) number?
What the …?
A married bachelor is a classic example of a logical contradiction. The very term "bachelor" means "unmarried male person". It is, strictly speaking, logically impossible for John to be a married bachelor. The only way around this is to get into pointless semantics, to suggest that married does not have to mean what it means, that bachelor could (in an alternate world) mean "person with a big nose" rather than "unmarried male person" - to suggest that, strictly speaking, language is fuzzy and we don't know for sure what any of the terms we are using mean and therefore anything is possible. This is a very clear indication that WLC is being a doofus.
In the midst of this doofusness, WLC uses the term "metaphysically impossible":
What your theology professor rightly argues is that the universe’s coming into being from nothing is metaphysically impossible. Philosophers typically call this sort of possibility broad logical possibility, in order to distinguish it from strict logical possibility. Speaking in terms of broad logical (or metaphysical) possibility, we claim that coming into being from nothing is broadly logically impossible, just as it is broadly logically impossible that something is colored but unextended or that gold has the atomic number 13.
Note that he's tried to tie "broad logical possibility" to "metaphysical possibility", and claim that "the universe's coming into being from nothing" is "broadly logically impossible" because it's "metaphysically impossible".
Nonsense. There are two ways of looking at metaphysical possibility. One is encapsulated in Kripke's classic statement "Water is not H2O" - this is metaphysically impossible because, by composition, water is H2O. This is closely linked to the other way of looking at metaphysical possibility, because there is no possible world in which water would be anything else than H2O, because that's what water is. The other view on metaphysical possibility is such that we might discuss other possible circumstances - so it's a metaphysical possibility that this would have been written in German, had the Allies not won World War 2, or in Russian is the USSR had won the Cold War.
For something to be metaphysically impossible (and thus "broadly logically impossible"), it could not have been - even if the world were different. Examples that we can conjure up for this category are usually the logically contradictory (the time traveller who accidentally kills his mother when she was a toddler), definitional (a sunny day with full cloud cover (our definition usually means at ground level, but above the clouds it is likely to be as sunny as any other day)) or mathematical (1=2). An example that doesn't quite fit into any of these is the reified privative, like a potful of donut holes (ignoring these sorts of donut holes) and the dark creeping into your house (along with the cold), but I am not sure that this constitutes a metaphysical impossibility, it seems to be more like a simple confusion.
So, when WLC claims that "the universe's coming into being from nothing" cannot be, because it's metaphysically impossible, he is very much begging the question. He gets away with it because very few make the effort to dig into precisely what metaphysical impossibility is.
Maybe he's not so much of a doofus after all. Just a big fat liar. I still think it's broadly logically possible (and thus metaphysically possible) that he's a lying doofus though.