Where does this argument fail?
(1) Necessarily , there is no evil in heaven (premise).
(2) If there is morally significant free will in Heaven, then it is not the case that, necessarily , there is no moral evil in heaven (premise, from free will defence).
(3) Therefore, there is no morally significant freedom in heaven.
(4) Heaven is a domain in which the greatest goods are realised (premise).
(5) Therefore, the greatest goods are realised in a domain in which there is no morally significant free will.
(6) A perfect being can choose to create any domain that it is logically possible to create (premise, appeal to omnipotence).
(7) Therefore, a perfect being can choose to create a domain in which the greatest goods are realised and in which there is no moral evil.
(8) A world that contains the greatest goods and no moral evil is non-arbitrarily better than any world that contains the greatest goods, incomparably lesser goods, and the amounts and kinds of evils that are found in our universe.
(9) If a perfect being faces a choice among options and one of those options is non-arbitrarily better than the others, then the perfect being will choose the non -arbitrarily better one.
(10) Therefore, it is not the case that a perfect being made our universe.
First of all, thank you to Philo for the question. Philo is trying to attack the free will defence, made famous by Alvin Plantinga. He does that by trying to show that there's no free will in heaven, and asserts that heaven is a better "world" than the earth we live on. Therefore, given a choice, he says that a perfectly good God would surely not have created this world (but created something much more like heaven).
I don't agree with many of the premises in this argument, and even if I did accept them, it seems to me that the argument is invalid (that is, that the conclusion doesn't actually follow from the premises). In my humble option premises (1), (4) and (8) are pretty much speculation, and to use (9) in the way it is would require an extra premise which seems unlikely to be true.
Personally I don't know whether or not free will exists in the universe, and much less if it exists in heaven. But Philo tries to prove that it doesn't exist in heaven in steps (1)-(3). The first premise, that there is necessarily no evil in heaven is subtle. Philo doesn't mean that there's no evil in heaven - but it is impossible for evil to ever be there.
I guess this is where we ran into the first problem. On Philo's view Satan couldn't have rebelled - which is almost the exact opposite to what Philo is saying. I think Philo would have to show that it was impossible for Satan to rebel in heaven.
There is also another common illustration of heaven that people think about. CS Lewis paints several pictures of heaven and hell in his books. But the clearest view is probably "The Great Divorce" where people are constantly given the choice of whether they want to forgive, and heal the hurts or whether they want to hold on to the grudges that hold them back.
On both CS Lewis view, and the traditional view of Satan rebelling premise (1) is in fact false. Now I'm not really wedded to either of these ideas, as both are pretty much entertaining speculation (from outside the Bible). But for the argument not to fall over, Philo would have to show both the traditional view of Satan rebelling, and CS Lewis' views are actually impossible.
Premise (4) seems unjustified too,
(4) Heaven is a domain in which the greatest goods are realisedEven though we colloquially say "Going to heaven", the Bible talks about the earth being renewed. On one view, the world is restored, the hurts becoming healed, and in the other (which Philo seems to be presenting) the world is done away with and we go and have some ethereal existence. It seems to me that the argument is only relevant if it is referring to Philo's view, whereas - at least from a Biblical point of view - it's not clear to me how it actually applies. If this world is something of a prerequisite, and it's not even clear they constitute two totally different "worlds". I'd be interested how Philo would you explain passages like 1 Corinthians 15, we are described like a seed?
On the other hand if Philo means this to refer to heaven in the traditional sense, containing only God, angels, and perhaps some martyrs as they wait for the new earth (again, this is all depends on how literally you can take visions) - I don't agree that it is the domain in which the "greatest goods" are realized. At very least, all of creation praising God, restored and reconciled is a tremendous good, which is completely missing if you only include heaven, and ignore the restored earth.
Premise (8), I also have problems with. This is getting long, so I'll just mention briefly that I'm not convinced that, in general, morality is a well ordered set - and it's often not possible to compare, or to say definitely that one is the best, strictly better than another. I'm not convinced in this situation, because whenever I think of it practically, there seem like there's a million ifs and buts which aren't justified here (such as having different types of good made possible in both worlds - and it seems hard to compare the two). There could be many options which are good, and would be open for God to choose whichever he liked.
But even if I accepted all these premises (I don't) - then the argument doesn't even seem valid to me. Point (9) says:
(9) If a perfect being faces a choice among options and one of those options is non-arbitrarily better than the others, then the perfect being will choose the non -arbitrarily better one.That's a pretty big "if". Traditionally, both heaven and earth exist together - so God doesn't face such a choice. Clearly he could create both. On a Christian view, he has. So, this is clearly not a choice which God faces. To make the argument valid, Philo would have to add the premise (or prove) that God actually faced this choice. Otherwise the argument isn't valid.
Thank you, Philo. I don't agree with your argument, but you've clearly put a lot of thought into it. I hope you (or anyone else) feels free to respond either on a blog, in the comments, or even on reddit! I look forward to continuing this with you.