Sunday, 18 December 2011

Glenn Peoples' moral argument for God

Glenn Peoples' blog has been interesting me lately. He has just out up his version of a moral argument for the existence of God.

Glenn argues, as does Craig:

If there's no God, there are no objective moral values.
There are objective moral values
Therefore there is a God.

Of course, Glenn realizes his premises, especially the first premise, will require considerable support, so he makes his case for it here.

Here's part of my comment on People's moral argument...

Glenn – I’m tempted to start investigating your argument more but it would be really helpful if you could set out the argument more formally, so that the most basic premises supporting your conclusion are clearly identified. Make it very clear why there is objective moral value only if there is an all-powerful, all-good, personal God. E.g. why moral Platonism won’t do, for example. Why non-natural objective moral facts won’t do either. Why it’s got to be a person. Exactly how the is-ought gap plays a role in delivering the conclusion. It would also be good to see what your assessment of the probability of each of the basic premises of the argument is.

Notice by the way that as more premises are introduced that you may consider to be much more probable than not – that have, say, an 80% probability of being true – the probability of your conclusion being true may nevertheless drop like a stone. With, say, just five required basic premises of 80% probability each, the probability that your conclusion is true drops to just 32%.

That’s to say, the probability that your conclusion is FALSE is nearly 70% (p.s. given just those premises).

(Wes Morriston also points this out, I believe)

However some theists (not you) are very good at disguising this problem of plummeting probabilities with amazing rhetorical flourishes!

Post Script.

In case it's not clear, I am pointing out that a deductively valid moral argument based on even say five basic premises with an 80% probability of truth each, produces a conclusion that has 68% probability of being false, given just those premises. It's much more likely to be false than true!

Now your moral argument, which you putting up against the problem of evil (which it apears you've entirely failed to deal with, and which itself renders the moral argument more or less useless, even if its first premise *could* be established), seems on the face of it to be based on a series of thoughts which you find fairly plausible which you think entail your God exists. But even if (i) your argument makes say just 5 basic assumptions with an 80% probability of truth each, and (ii) they do collectively deductively entail your god exists, your argument is still a dismal flop.

I asked that you clarify what your argument is so we can check if this obvious seeming flaw in your argument is really there. But you say you haven't got the time.

POSTSCRIPT 21 DECEMBER. I have just added this comment...

Glenn and others want to create a smokescreen of technicality to disguise the fact that his argument, looks, prima facie, like a dismal flop given its based on a series of "more probable than not" premises. The rule I am applying is: to get the highest probability you can assign to the conclusion in a valid deductive argument, you just multiply the probabilities of the basic premises.

Now yes, there are some exceptions to this general rule. So for example, when a premises is redundant, like so: A, B therefore A. Here, you don't factor in the probability of B, for obvious reasons. Also, when the conclusion is a tautology, its probability will be 1, irrespective of the probability of the premises (though the premises are then all redundant, of course). Also, simple multiplication is not appropriate where there's a logical or known causal connection between premises. The probability of the conclusion may then be either higher or lower than the figure you get by simple multiplying. E.g.

A is male
A is female
Therefore A is male and A is female.

Given our background knowledge that being male makes it highly unlikely you are female (unless a hermaphrodite), it's clear we should not give a value of 26% to the conclusion given a prob of 51% to each premise. The probability is LOWER than you get by simply multiplication. Given that further background knowledge. Ditto (and here the we’re dealing with logical exclusion – the conclusion has a mathematically guaranteed probability of 0):

A is 60 years old
A is 61 years old
A is 60 years old and A is 61 years old.

Other times the probability of the conclusion can indeed be higher.

So yes, there are exceptions to the rule. But the point is they are exceptions to a general rule that does otherwise generally apply and which we'll be entitled to suppose applies in the case of Glenn's moral argument too, unless Glenn can explain why it doesn’t. At this point, we cannot tell for sure, because Glenn won’t even clearly set out what the basic premises of his argument actually are. In which case, we should just shrug and walk away. Glenn’s given us nothing.

Incidentally the “upper bound” stuff, while it looks awfully impressive especially when articulated using long strings of formulae, appears to be based on some rather dubious ideas. I cannot find any reference to it outside of theistic circles (e.g. Tim McGrew). Can you point me to some?

Craig’s reference to it is opaque, btw, in the context of what he says. That looks like an attempt to baffle with bullshit.

But I note in any case that the “upper bound” point, even if it is correct, appears to give us no reason at all to suppose that we cannot, on the basis of saying that Glenn’s basic premises are five with a probability of 0.8 each, draw the conclusion that the probability of his conclusion cannot reasonably be estimated as higher than 0.32, given knowledge of just those premises. Indeed, that’s exactly the conclusion we’re usually entitled to draw in such cases (noting, of course, that there are indeed a few exceptions – perhaps Glenn will say “God exists” is a tautology? In which case the premises will have a lower probability than the conclusion but will be redundant!). So why not in this case? That’s what Glenn would need to explain, once he’s actually identified what his premises are (hint: Glenn might insist there’s some connection between the premises that means the probability of the conclusion should be higher – but the onus is surely then on him to identify this connection). Remember, I am not saying the probability of Glenn’s conclusion will be low. I am saying that if it’s based on a series of merely more-probable-than-not basic premises then (unless this is some sort of special case – see above) the probability of the conclusion cannot be considered, on that basis alone, very high.

POST SCRIPT 23 DEC. Well, I have been getting clearer about how all this upper bound of 1 stuff works, largely thanks to Tim (McGrew?) who is v knowledgeable about it and has been commenting on Glenn's website. It now seems to me that the logic concerning an upper bound of 1 is indeed impeccable. And, it turns out, once all the logical symbolism etc. has been unpacked and understood, completely irrelevant to the point I'm making.

I'll explain exactly why in another full post. It's important to get this stuff straight because, if I am correct, saying "Ah but that's just the lower bound of the probability; the upper bound of the probability of the conclusion is 1" in response to the objection that the probability of the conclusion (assuming independent, non-redundant premises) given just validity and the probabilities of the premises is just those probabilities multiplied, is a complete red herring (indeed, the person who says this is committing the straw man fallacy).

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