Friday, November 17, 2006

Problems for the Fine-Tuning Argument

By my lights, the following considerations are sufficient to show that the argument from fine-tuning fails to make theism more likely than not.

There is an equally good, rival explanation of the apparent fine-tuning of our universe. For the fine-tuning for life would be equally well explained if our universe were embedded in a vast “sea” of infinitely many other universes.[1] Imagine a natural process or mechanism that continually generates universes (call it a 'cosmos generator') – perhaps something like a giant quantum field. Each time it pumps out a universe, it gives a random combination of values to its fundamental constants of nature. So on this hypothesis, infinitely many other universes exist – or at least lots and lots – and each one has a different set of values for its fundamental constants. Most of these universes have no life, since only a few possible combinations of values of the constants are life-permitting. But some do (e.g., ours). If so, then the explanation for why our universe is "fine-tuned" for life is that we exist in one of those few cosmoi – out of the trillions upon trillions of cosmoi that exist -- that has the “right” combination of values. This hypothesis is just as good as the hypothesis of intelligent design, since it's a hypothesis that explains all of the same data; so we have no persuasive reason to prefer the hypothesis of intelligent design to this one.

Objection 1: We've never seen such a multiverse, and we have no good evidence that it exists.

Reply: This objection fails to see that the point of constructing these theories in the first place is precisely because we have no way of directly observing the cause of the apparent fine-tuning of the fundamental constants of our universe. And it's just part of the nature of such theories that they accrue probability just to the extent that they can explain the range of data in question. Thus, it's not true that we have no evidence that a multiverse exists. Rather, the extent to which it can explain the data *just is* the grounds for according it some degree of probability. And the same is true of the theistic hypothesis, of course -- we only have reason to think that *it* is probable to the extent that it can explain the data of apparent fine-tuning. That's what the theory-data relationship is all about.

Obection 2: The hypothesis of a cosmos generator only pushes the problem of apparent fine-tuning back a step. For a cosmos generator would be a very complex and intricate process/mechanism. If so, then we would need an explanation for the fine-tuning of the cosmos generator itself.[2]

Reply: (i) Of course, we can just stipulate that, as a part of our hypothesis, the cosmos generator has its laws and constants *of necessity*, i.e., that there is only one possible set of laws and constants for the cosmos generator. It’s not important that this stipulation is independently known to be true; it need only be a hypothesis with no features for which we have independent reason to think false or impossible. Why is it ok to make these stipulations? Because it's a *theory* constructed to explain a range of data, and that's just the way it is with theories in general. And notice: This is both true of this hypothesis and the designer hypothesis -- both theism and naturalism are treated in the argument as sort of large-scale scientific hypotheses that were generated to explain some fundamental features of the universe. (ii) But even if one rejects the "necessary laws" stipulation -- i.e., that the laws governing the nature and functioning of a cosmos generator must be contingent -- the objection is still pretty dubious. For it's an objection that applies equally well to the theistic hypothesis. For both hypotheses grant that there is some brute, unexplained order that can have no further explanation -- the structure and the laws governing the cosmos generator on the naturalistic hypothesis, and the intellect and will of God on the theistic hypothesis.[3]

Objection 3: OK. But even if we grant that both hypotheses are saddled with some brute order that can have no further explanation, still, the theistic hypothesis is *simpler* than the naturalistic “cosmos generator” hypothesis. For on the cosmos generator hypothesis, the explanation of the apparent fine-tuning of our universe requires that there are lots and lots of other universes -- perhaps infinitely many. By contrast, the theistic hypothesis explains the apparent fine-tuning of our universe in terms of just a single entity: the god of traditional theism. Thus, even granting that theism leaves unexplained and brute at least *some* order (God's intellect and will), it's a much more economical/parsimonious explanation of the data of apparent fine-tuning.

Reply: The objector mistakenly assumes that there is only one kind of theoretical parsimony, viz., *quantitative* parsimony (i.e., the explanation postulates fewer entities). However, as David Lewis has taught us, another type is *qualitative* parsimony (i.e.,the explanation postulates fewer *kinds* of entities). And while the theistic hypothesis is a much more *quantitatively* parsimonious explanation of the data (it explains all of the data in terms of just one entity, viz., a god), the naturalistic cosmos generator hypothesis is a more *qualitatively* parsimonious explanation of the data (since it explains all of the data solely in terms of one *kind* of entity, viz., material objects). And it's not clear which type of theoretical parsimony is more important here.

Thus, it seems to me that the theistic and multiverse hypotheses are roughly equally likely given the data of fine-tuning.
[1] This line of reasoning is based on Peter Van Inwagen's in his Metaphysics, 2nd edtion (Westview, 2002).

[2] Notice that this is precisely the naturalistic version of the objection to the design argument that the theist is unwilling to countenance as legitimate to her own hypothesis of design (i.e., the "who designed the designer?" objection).

[3] This seems to me where the real force behind the "who designed the designer?" objection lies: both theism and naturalism are saddled with at least *some* brute order; so why fault naturalism with a "problem" that applies equally well to theism?

Design Arguments: Old and New

The Design Argument

There are two broad forms of the design argument:

1.The Classical (“Old School”) Design Argument:

Paley’s is the most important version of the classical design argument. This version is an argument from analogy. It typically appeals to living organisms and their parts as cases of apparent design. The line of reasoning here can be put as follows:

We come to learn through experience whether an object has been intelligently designed. How do we learn to detect design? Well, over a long course of experience, we notice a constant conjunction of a cause of one type (intelligent designers) producing an effect of a certain type (complex objects whose parts work together to perform a function). Thus, after a while, we no longer have to observe a person designing an object in order to know that the latter has been designed. Rather, we can then legitimately *infer* that, say, a watch was fashioned by an intelligent cause. For we can then justifiably base such an inference on an inductive argument based on the observed constant conjunction of the cause-type of intelligence and the effect-type of complex objects whose parts work together to perform a function.

Now for the punchline. If we have come to know, via uniform experience, of this constant conjunction of intelligent causes producing the effect of complex objects whose parts work together to perform a function, then what must we conclude about living organisms and their parts -- things such as the marvelously intricate structures of cells, eyes, bird's wings, whole organisms, and even whole ecosystems? For these resemble the artifacts that we know to be designed, in that they, too, are incredibly complex entities whose parts work together to perform a function. For Pete's sake, think of the workings of a cell! We now know that it's functionally equivalent to (in the words of Michael Denton) "a self-replicating machine factory"! Thus, since living things relevantly resemble human artifacts, and the latter are intelligently designed, then we can't rationally avoid concluding that the former are intelligently designed as well.

In short, our basis for thinking that objects such as watches, cars, and computers are designed is an inductive inference based on our experience of a constant conjunction of a certain type of cause (intelligence) and a cerain type of effect (complex objects whose parts work together to perform a function). And our grounds for thinking that living organisms and their parts are designed is based on an argument from analogy between watches, cars, and computers on the one hand, and living organisms and their parts on the other.

The argument can be expressed as follows:

1. Human artifacts are intelligently designed.
2. Living organisms and their parts relevantly resemble human artifacts (in that they both are complex and their parts that work together to perform a function).
3. Therefore, probably, living organisms and their parts are intelligently designed as well.

This form of the design argument is seldom used today, due to a number of criticisms. But the most forceful criticisms come from David Hume (see his masterful Dialogues Concerning Natural Religion), and Charles Darwin.

Some of Hume's most forceful criticisms are these: (i) since the argument is an argument from analogy, the likelihood of the conclusion turns one the degree of similarity between the two things compared in the premises. Unfortunately, the degree of similarity between artifacts and organisms is too low to warrant a confident inference to the intelligent design of the latter; (ii) even if they were simillar enough to infer design, the conclusion wouldn''t justify an inference to full-blown theism -- let alone orthodox Christian theism. Thus, even if the argument worked, it wouldn't show that the designer is immaterial, all-powerful, all-knowing, perfectly good, or even that there is just one designer; nor would it show that the designer is the creator and/or sustainer of the universe -- or even that the designer still exists.

But the most forceful criticism appears to be the one from Darwin -- i.e. the strong empirical evidence for biological evolution. If biological evolution is true, then the complex, apparently purposive structures and organisms we find in the biological realm don't require explanation in terms of (at least) the direct causation of a divine designer (although we'd need another explanation of the *origin* of living organisms, since the latter wasn't the result of mutation and natural selection. Whether there is or could be a natural explanation for the origin of living things, I don't pretend to know).

However, philosophers have come up with a new version of the design argument, one that doesn't fall prey to most of these objections, viz.:

2. The Contemporary (“New School”) Design Argument:

This version is not an argument from an analogy, but rather an abductive inference to the best explanation (and thus isn't subject to the "weak analogy" objection). For purposes of simplicity of discussion, we can say that, roughly, one hypothesis H1 is a better explanation of a range of data D than another hypothesis H2 if we would *expect* D more if H1 were true than we would if H2 were true.

According to this version of the design argument, then, certain features of the universe are treated as data, and then various hypotheses are offered to explain the data. It typically appeals to non-living aspects of the universe as cases of apparent design (and thus isn't subject to the "evolution" objection). The most common sorts of phenomena appealed to in such arguments is the range of fundamental constants of nature -- in particular, the extremely precise values they have, and must have in order for life to arise in the universe.

There are anywhere from 20 to 50 (or so) such features of the basic structure of the universe. Each of these has to have a mind-bogglingly precise numerical value in order for life to evolve in the universe. The following is a small sampling of these features:

-the strong nuclear force: this is the force that binds protons and neutrons together within the nucleus of the atom.

-If the strengthened or weakened by 1% or more: would reduce the amount of carbon and oxygen produced by stars, so that carbon-based life would not be possible; nor would any oxygen-breathing organisms be able to exist.

-the weak nuclear force: this force controls, among other things, the fusion of protons. It’s current strength prevents stars from exploding, and allows them to burn slowly.

-if slightly weaker: stars wouldn’t produce the requisite light, heat, and heavy elements. The universe would be largely composed of just helium

-if slightly stronger: stars wouldn’t produce the heavy elements

-the cosmological constant: this constant relates to the rate of expansion of the universe due to the Big Bang.

-If expansion rate were increased by more than one part in 10120: matter couldn’t clump together to form galaxies. This would mean no stars, which would mean no planets, and thus no habitat for life to exist

-If the expansion rate were decreased by more than one part in 10120: all of the matter in the universe would clump together into one giant clump before the relevant types of stars could form

-other examples include the strength of gravity, the mass of a proton, the fine structure constant, the electromagnetic force constant, and the total density of the universe.

If the numerical values of these, and any of the other constants, were increased or decreased – often just by a fraction – then no life at all could have arisen in the universe. Thus, it looks as though the basic structure of the universe has been “fine-tuned” in order for life to evolve within it.

The two hypotheses typically proposed to explain the data of fine-tuning above are (i) intelligent design and (ii) non-intelligent, natural causes. Thus, the Best Explanation version of the design argument can be expressed as follows.

Let ‘D’ denote some range of phenomena or data that needs explaining. For example:

D: The universe is fine-tuned for the existence of life (i.e., there are a large number of fundamental constants of nature. The value had by each of these is contingent, and independent the others. Each value is just one among an extremely large range of possible values, and each constant had to be assigned the value it has (or one very, very close to it) or no life would have arisen in the universe.)

Let ‘H1’ and ‘H2’ denote competing hypotheses offered to explain D:

H1: The fine-tuning of the universe is due to intelligent design.
H2: The fine-tuning of the universe is due to non-intelligent factors, such as chance and necessity.

Then we can state the abductive, inference-to-the-best-explanation version of the fine-tuning argument simply as follows:

1. The truth of H1 would lead us to expect D, but the truth of H2 wouldn’t lead us to expect D.
2. Therefore, H1 is a better explanation of D than H2.

Thursday, November 16, 2006

Outline of the Standard Evangelical Case for the Reliability of the New Testament

I'll probably return to this post a lot to fill in the details and provide explanation, but I just wanted to put something on my blog that provides a way to see the standard case at a glance.

The Reliability of the Orthodox “Portrait” of Jesus according to Evangelicals: The Basic Case[i]

1. From our Current Bibles to the Church Fathers: Textual Criticism
1.1 The Argument from Textual Criticism
1.2 The Argument from Patristic Quotation

“Okay, that gets us back to within a few centuries of the life of Jesus. But how do we know that our information about Jesus wasn’t corrupted prior to that?”

2. From the Church Fathers to the Gospels: The Argument from Patristic Testimony of Apostolic Authorship

“Okay, but the case for apostolic authorship is shaky and widely rejected. Are there other reasons to think that the gospels give us reliable eyewitness testimony about Jesus?”

3. From the Gospels to Their Immediate Sources:
3.1 The Argument from Markan Priority and the Dating of Luke-Acts
3.2 The Argument from Source Criticism: Mark, Q, M and L
3.3 The Sherwin-White Argument for a Stable Reliable Core of Information

“Okay, that gets us to information about Jesus that’s about two to three decades old, and many believe that the circumstances of the NT make Sherwin-White’s argument inapplicable in this case. Are there other reasons to think that such information is reliable?”

4. From the Gospel’s Immediate Sources to the Oral Tradition
4.1 The Argument from the Nature of Jewish Oral Tradition[ii]
4.2 The Argument from Studies of Oral Cultures
4.3 The Argument from Aramaisms
4.4 The Argument from Poetic Forms
4.5 The Argument from a Pre-Easter Tradition

“Okay, if these arguments work, then there is a general presumption of reliability in favor of the gospel materials, since they are based on reliably-preserved eyewitness information that goes back to the time of Jesus. But these arguments are widely disputed. Are there other reasons to believe that the sources behind the gospels are reliable if we’re not convinced by them?”

5. From the Oral Tradition to Jesus: The Argument from the Criteria of Authenticity[iii]

“Okay, but many people dispute that the criteria of authenticity establish the reliability of the quantity of passages that you claim. What if they’re right and many passages don’t give us reliable information about the words and deeds of Jesus?”

6. The Worst Case Scenario:
6.1 The Argument from the Minimal Core of Passages Accepted by the Radical NT Critics[iv]
6.2 The Argument from Coherence with Ancient Creeds and Hymns Preserved in the Epistles

[i] This case can be found in, for example, Blomberg’s The Historical Reliability of the Gospels (and summarized in chapter form in several apologetics books), Marshall’s I Believe in the Historical Jesus, the relevant chapter in Moreland’s Scaling the Secular City, Blomberg’s chapter in Craig’s Reasonable Faith, and Boyd’s Cynic Sage or Son of God?.

[ii] After this point, it’s often argued that a presumption in favor of reliability is established, and so the burden of proof is on anyone who challenges the inaccuracy of a given passage. In the next section, an argument is given to show that even if one is not convinced that this is true, general reliability can be established via the criteria of authenticity while constantly having to shoulder the burden of proof. Thus, there is a dilemma: either the burden of proof is established here or it isn’t. If it is, then in each case reliability can be upheld by argumentation when challenged. If it isn’t, then in each case reliability can be established by proper application of the criteria of authenticity. Either way, then, the gospels can be shown to be reliable. Blomberg often uses this argument, but I think it goes back to at least Marshall.

[iii] At this point, many apologists (e.g., Moreland) argue that even if one is still unconvinced of general reliability, the minimal set of authentic sayings widely accepted by most NT critics still prevents total skepticism about knowledge of Jesus. For even if you only accept sayings that pass the criterion of dissimilarity -- which even the most radical NT critics accept as a reliable tool for gleaning historical information -- you are still left with most of the parables some other sayings. These are about the kingdom of God and Jesus’ relation to it. And this picture of Jesus is in keeping with the orthodox one. Thus, no matter which way you slice it, the NT gives us a reliable picture of Jesus.

[iv] Which is usually based upon just the use of the criterion of dissimilarity.

Monday, November 13, 2006

Some (Temporarily) Final Thoughts About the Free Will Defense

I'm more than happy to discuss Plantinga's Free Will Defense further with those interested (see previous post), but for now, here's my tentative summary and conclusion on the matter, prefaced with some contextual stage-setting:

A standard way to state the deductive argument from evil is the one we've inherited from Hume in his Dialogues Concerning Natural Religion (who in turn inherited it from Epicurus):

"Is he willing to prevent evil, but not able? then is he impotent. Is he able, but not willing? then is he malevolent. Is he both able and willing? whence then is evil?"

The reasoning here can be teased out as follows:

1. Evil exists. (Premise)
2. If God exists, then God is omnipotent, omniscient, and perfectly good. (Premise)
3. If God is omniscient and omnipotent, then He is able to prevent evil. (Premise)
4. If God is perfectly good, then He is willing to prevent evil. (Premise)
5. If God is willing and able to prevent evil, then evil does not exist. (Premise)
6. Therefore, God is not both willing and able to prevent evil. (From 1 and 5)
7. Therefore, God is not omnipotent, omniscient, and perfectly good. (From 3, 4 and 6)
8. Therefore, God does not exist. (From 2 and 7)

A standard response to the argument is the appeal to free will: God takes no delight in robots; he wants a community of persons who have the ability to freely enter into a relationship with himself and others. Furthermore, he wants a world that contains not just aesthetic beauty, but also moral goodness that's grounded in the free actions of his creatures. But the latter is a great good that can only be gotten by creating free creatures in the first place. But once you do that, you must allow for the possibility that they'll abuse that freedom and freely choose to do wrong. That is, it's logically impossible for God to *force* his creatures to *freely* do right. Thus, since it's no limit on omnipotence to be unable to do the logically impossible, premise (4) is false, and the argument is unsound.

But then along came J.L. Mackie. He pointed out that if a person is free to do wrong, then it follows that it's possible for such a person to freely do right. Thus, there are possible worlds at which people freely do right at least some of the time. And if it's possible to freely do right some of the time, then on the basis of the same sort of reasoning, it's possible for free creatures to always freely do right all of the time. Thus, there are possible worlds in which free creatures always freely do right. But if so, then contrary to the old version of the free will defense, it's not beyond God's omnipotence to create a world in which free creatures always do right, in which case premise (4) remains unscathed, leaving the deductive argument from evil unrefuted.

But then along came Alvin Plantinga. In God and Other Minds, in The Nature of Necessity, and in God, Freedom, and Evil, he took issue with Mackie. In particular, he argued that Mackie falsely assumes that God can do whatever is logically possible (Plantinga calls this assumption, "Leibniz Lapse"). But this claim is false -- there are possible worlds that not even an omnipotent God can actualize. So, for example, suppose that in some possible world W, some person -- call him "Steve" -- freely chooses to do something morally wrong. Then it's not possible for God to actualize **W** (that very world) and yet prevent Steve from doing the wrong action. For the counterfactuals of freedom are fixed by what people freely do in a given possible world, and are thus restraints on what God can do at that world. Plantinga took this insight about counterfactuals of freedom and used it to develop his notion of "transworld depravity" (or'TWD' for short). In a nutshell, and very roughly, a person suffers from transworld depravity if, among the worlds *that God can actualize*, that person would perform at least one wrong action *in those worlds* -- the God-actualizable worlds -- no matter what circumstances or sequence of circumstances God puts them in.

Now it turns out that there are two basic interpretations of TWD in the literature: what I'll label as 'the 80's interpretation' and 'the 90's interpretation'. According to the 80's interpretation, a person suffers from transworld depravity just in case they would freely do at least one wrong thing in *every* God-actualizable world. But according to the 90's interpretation, the definition is relativized to a given possible world: a person suffers from transworld depravity *in a given world W* just in case God can't actualize **W** (including any of the worlds *counterfactual* to W) without that person performing at least one immoral action. This is a much more convoluted account than the 80's interpretation. Perhaps the simplest way to put it is this: Suppose you exist in possible world W1, and you are transworld depraved at W1. Then no matter what God could have done *at W1* (and at worlds *counterfactual* to W1 ) in order to ensure that you always freely do right, it won't work -- you'll blow it at least once.

The two interpretations differ in that the 80's version makes free creatures out to be transworld depraved in all possible worlds in which they exist -- i.e., as an ordinary essential property. However, the 90's interpretation is more subtle. It takes transworld depravity to be a *contingent* property of free creatures: they're transworld depraved at some worlds, but not at others. Furthermore, according to the 90's interpretation, transworld depravity is defined in terms of *counterfactual worlds* -- i.e., just the worlds counterfactual to a given world W -- while the 80's interpration defines it in terms of ordinary possible worlds.

With these distinctions in mind, we can now see the main idea of Plantinga's Free Will Defense: What if *every* possible free creature suffers from transworld depravity? That is what if:

(<> TWD) Possibly, every creaturely essence suffers from transworld depravity.

According to the 80's interpretation, this means that for all we know, every world that it's in God's power to create will have at least one free creature that performs at least one morally wrong action. If so, then God's hands are tied as to what worlds he can create. In particular, he would be unable to create a world with free creatures (and thus moral good) without also creating a world that contains moral evil. If so, then even though there are possible worlds at which free creatures never do wrong, God can't create any of them. But if not, then Premise (4) is false, and the deductive argument is unsound -- or at the very least, we can't rule it out as false that it's possible that every free creature suffers from transworld depravity, in which case premise (4) is at least dubious.

According to the 90's interpretation, the implications are a bit different. It implies that for all we know, there is at least one possible world W at which all possible free creatures exist, such that no matter what God could've done at W, at least one free creature there performs at least one wrong action at W. If so, then God's hands are tied with respect to what he can do *at W*. In particular, he would be unable to create *W* with free creatures (and thus moral good) without W also containing moral evil.

Now in light of the above, and in light of my previous posts, it seems to me that the Free Will Defense is subject to the following dilemma:

Either the 80's interpretation of transworld depravity is correct or the 90's interpretation is correct. Now if the 80's interpretation is correct, then (<>TWD) is only weakly epistemically possible at best (for non-theologically conservative Christians) and flatly false at worst (for theologically conservative Christians) -- either way it's not a successful defense against the deductive argument from evil (see my "On the Force of "Possibly" in Plantinga's Free Will Defense" for the details of the argument for this horn of the dilemma).

On the other hand, if the 90's interpretation of transworld depravity is correct, then (<>TWD) is subject to the following to criticisms (See my last post for the sources in the literature for these criticisms):

(i) Plantinga hasn't succeeded in showing that such a world (i.e., a TWD world) is *metaphysically* possible. To see this, consider the following: for all we know, it's possible that, necessarily, some essence or other is blessed with *transworld sanctity* (TS). But if we can't rationally rule this out, then since it's incompatible with (<>TWD), then we're only justified in taking (<>TWD) to be *epistemically* possible at best.

(ii) But more importantly, even if we grant that (<>TWD) is metaphysically possible, the correct response would then be,"so what?" If TWD is true at W, then this only prevents God from actualizing free creatures who never blow it *if* he freely chooses to actualize *W*. But there are *other* possible worlds at which free creatures don't have these cruddy counterfactuals of freedom, and thus always freely do what is morally *right*. If so, then Mackie's objection remains: why didn't God actualize one of these *other* worlds?

Therefore, on either interpretation, apologists are being misleading when they claim that Plantinga has refuted the deductive argument from evil. At best, he's shown that we can't be confident that the deductive argument from evil is sound.

Friday, November 03, 2006

On the Force of "Possibly" in Plantinga's Free Will Defense (Slightly Revised)

Plantinga construes the key claim in his Free Will Defense as possibly true:

(TWD) Possibly, every creaturely essence suffers from transworld depravity.

According to Plantinga, if a creature suffers from transworld depravity, then *every* God-accessible world (i.e., every world *that God can create*)) is one at which the creature goes wrong at least once.

So if some free creature FC is transworld-depraved, then we have:

1) Necessarily, if God actualizes FC, then FC goes wrong at least once.

And if every creature is transworld-depraved, then we have:

2) Necessarily, for any x, if x is a free creature, then if God actualizes x, then x goes wrong at least once.

If so, then if Plantinga is using "possibly" in (TWD) in the metaphysical sense (as in (1)), then (TWD) amounts to:

3) Possibly, it's necessary that for any x, if x is a free creature, then if God actualizes x, then x goes wrong at least once.

But Plantinga accepts S5 modal logic. If so, then he accepts the following axiom of S5 modal logic:

(AS5) If it's possible that P is necessary, then P is necessary.

But if so, then by (3) and (AS5), (TWD) reduces back to (2):

2) Necessarily, for any x, if x is a free creature, then if God actualizes x, then x goes wrong at least once.

But this can’t be what Plantinga meant to assert, can it? For now we don’t just have a defense – we have a theodicy. For we have an account that’s not just possibly true, but necessarily true. And you can’t have a stronger theodicy than one that’s necessarily true.

The problem, though, is that it’s implausible to think that (2) is true: is there some shortage of souls, such that there is no possible creaturely essence, such that there is at least one possible God-accessible world at which it never sins? Plantinga grants that there are possible worlds at which free creatures never sin; it’s just that none of them are worlds that God can actualize. Is this really plausible?

I think that this problem (in addition to some things that Plantinga says) leads many to say that Plantinga's "possibly" shouldn't be construed as *metaphysical* possibility (i.e., that there is, as a matter of fact, at least one possible world at which it's true), but rather as *epistemic* possibiliity (i.e., *we can't rule it out*, given all our evidence, that it's metaphysically possible).

Now the relevant notion of epistemic possibility can be construed in at least two ways:

(Strong EP) We're not quite justified in thinking that P really is metaphysically possible; however, we're not justified in thinking that P is metaphysically impossible, either -- given our evidence, it could go either way.

(Weak EP) We're not justified in thinking that P is possible; however, although it's implausible to think that P is possible, we can't *conclusively* rule it out that P is possible.

Of course, the theist hopes that (TWD) is at least strongly epistemically possible; if it's merely weakly epistemically possible, one wonders how interesting the Free Will defense really is ("Sure, it's pretty far-fetched to think that every essence suffers from transworld depravity, but it hasn't been *conclusively* ruled out as imposssible -- hooray!")

The problem is that the same objections arise all over again for the strong epistemic possibility construal: it seems implausible that it's metaphysically possible. It seems that there are infinitely many free creaturely essences that God could actualize; are we to think that *every one of them* is such that *all* of the worlds in which they always freely do right are inaccessible to God? And as I’ve mentioned before, it looks to be a part of conservative Christian theology that angels exist, are free, and that some never sin. But if so, then it’s not necessarily true (because it's not *actually* true) that all free creatures are transworld depraved. Thus, it looks as though it might not be an option for theologically conservative Christians to believe it’s strongly epistemically possible. Even if the Old and New Testaments don't force belief in a doctrine of sinless angels, it needs to be pointed out (again) that Christians who endorse Plantinga's Free Will Defense have no choice but to reject such an idea.

What about weak epistemic possibiity: is it true that we can't *conclusively* rule it out that every creaturely essence would freely go wrong in all God-accessible worlds? Well, maybe for non-theists, some non-Christian theists, and some moderate and liberal Christians. But it doesn't seem to be weakly epistemically possible for theologically conservative Christians (recall the problem of angels who always freely do right).

What, then, does Plantinga's Free Will Defense really show? In light of the previous discussion, just this: for people who aren't theologically conseverative Christians, it's not conclusively ruled out as impossible that the Free Will Defense saves theism from the logical problem of evil; but for the theologically conservative Christians, it seems that it is.
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