This is the twelfth of 17 posts, which are collectively Eternity, etc.
......As well as all those (correct) statements (see previous post), there are also a lot of truths about other metaphysically possible worlds [i]. Statements of the former kind naturally seem more important than truths about merely possible worlds; and I have not shown that not knowing the former would not make God liable to make mistakes. But balancing the possibility that they do is the possibility that such ignorance is required for our genuine freedom [ii]. And in any case, would it follow from God being maximally knowledgeable—as well as maximally powerful—that He is timeless even if He could only be completely knowledgeable about the future if He was timeless?
......Since the answer is no [iii], let us consider all metaphysically possible worlds, not just this one, under each candidate conception of God. And since God’s omniscience may be less certain than His omnipotence (see section II), let us consider His power as well as His knowledge. And in view of section IV, let us compare libertarian atemporalism with Presentist Open Theism, taking both those conceptions to be prima facie logical possibilities [iv].
......God being possibly timeless means that a world like ours could conceivably be the 4-dimensional creation of a God who transcends its temporal dimension. But it is therefore conceivable that a Presentist God could instantaneously make a 4-dimensional world that is similarly like ours—as it has been so far, and happening also to be that way in the future—but with a fourth dimension substantially unlike Presentist time [v]. So a world as ours would be were God timeless could conceivably be made by Him whether He is timeless or not. And He would be completely knowledgeable about it whether He made it or not.
......Similarly, for any possible spatiotemporal world that a timeless God could make, a Presentist God could conceivably make—and so would know all about—an isomorphic world. But Presentist Open Theism being possible means that this world might have a future that is open, in the sense that there are statements that are neither true nor false but which will be either true or false. And a timeless God could hardly make such a world, because for Him the future has to be completely real.
......Now, atemporalists may not regard that inability as detracting from His omnipotence, whether or not the creator of such a world would be liable to bodge things up in it. But there is also an argument that there are many more metaphysically possible creations if God is able to change (see section VIII), which uses what is shown in the next three posts, that there is no immutably complete totality of all the metaphysically possible whole numbers.
......[i] That is clearly so under Open Theism; and although the deliberate creation of something contingent seems to require several real possibilities to choose between, as well as a single actuality amidst counterfactuals, and hence some sort of change, creation is also taken to be contingent by Mawson, Belief in God, p. 71.
......[ii] Boethius famously argued that our freedom would not be limited by God’s knowledge of what we will be doing were that, not so much foreknowledge, as timeless knowledge (the analogy was with someone knowing what we do, not before we do it, but as we do it). (E.g. see Mawson, “Divine eternity,” pp. 38–40; Sorabji, Time, Creation and the Continuum, pp. 254–6.) Nevertheless, it would still have been true in the past that God knows (timelessly) all about the future. And to see why that might be a problem for libertarian atemporalism, consider a timeless God revealing truths about our future free actions to some of His saints in the remote past (and perhaps even on a distant planet). Is it obvious that our now being responsible for our actions could depend upon Him having done no such thing? (For more details, see Helm, Eternal God, p. 101 ff.)
......[iii] To see why not, consider someone choosing between Open Theism and the hypothesis that she was made by a transcendent computer, which has a complete database on (and complete control over) its creatures’ relatively virtual lives. Only the computer could be completely and infallibly knowledgeable about her whole life. But it would clearly be less knowledgeable (and powerful) than those who might have built an isomorphic computer, and who might have been created by an even more knowledgeable (and powerful) Open God.
......[iv] Cf. Mawson, “Divine eternity,” p. 46 n. 10.
......[v] If this world had been made like that, we should think of Presentism as false, because the analogical—as we should then see it—instant at which God was fully present would then include the past and future. Such a God would be neither everlasting nor timeless (see note vii of Divine Attributes cont.), but is also relatively implausible (see note iii of Omniscience Again cont.).