Must God choose the best?

If God is supremely good then he could only choose those possible outcomes, instantiate those possible worlds, which are consistent with his having his character, since to act inconsistently is a defect which God could not have. And since God is supremely good it must be supposed that God chooses from all possible worlds that world which is the best, the best of all possible worlds, since to suppose that he might choose a world which was less than the best is to suppose that he might do something which was inconsistent with his supremely good nature. P. Helm, Eternal God (Oxford, 2^nd ed., 2010), 172.

I agree with the first sentence, but I disagree with the second sentence. The paragraph is set up as if the first sentence is the premise, to which the second sentence is the conclusion. But there’s no connecting argument to show how the second sentence derives from the first. No reason is given as to why, if God is supremely good, he must choose the best possible world. That implication is assumed rather than explained.

What’s the implicit argument? It seems to involve a type of symmetry between God and the world, where the greatest conceivable being must choose the greatest conceivable world.

i) If that’s the argument, then it’s equivocal. Any created order is bound to be inferior, both in kind and degree, to God. So there’s no direct correlation between the excellence of God and the excellence of the world. There will always be a mismatch. The world will never come up to God’s level of perfection. Not even close.

ii) Moreover, a lesser possible world might encapsulate a unique or distinctive good that isn’t captured by a greater possible world. So even assuming there’s a best possible world (a very dubious assumption), the best possible world won’t necessarily be better in every respect. The best possible world might well be inferior to a lesser world in one or more respects.