Thanks Paidion, I agree, I think both those quotes are very useful to the discussion of “aiōnios” 
MacD would argue that the atheist who does the will of God (so far as God reveals to him, which the atheist may not recognize as being from God) is being faithful to God in the way that pleases God most, setting in opposition the nominal Christian who does not do the will of God whom we know from testimony (including most importantly from Jesus) is condemned as maximally as anyone can be condemned (however much that may be).
Lewis’ fictional example of Emeth, in The Last Battle, is borrowed directly from MacD’s notion here; and both were probably thinking of Romans 2 and the judgment of the sheep vs. the goats, among other things. Emeth wasn’t merely an atheist, he was nominally a Satanist!–but he was being faithful to God, and God accepted his real faith. Most Christians today would say Lewis illustrated the principle correctly (if extremely) with Emeth.
(This doesn’t get into God’s side of the account of faith, of course, which practically all Christians would agree is more important than whatever it is we’re doing.)
That’s Heb 11:6, by the way, for those following along at home.
The Greek (which is solidly attested in the text) is a bit different: “Now apart from faith (it is) impossible to well please (God), for the one coming to God must believe that He is and is becoming a Rewarder of the ones seeking Him out.”
This applies to those, like Enoch (the most special of special cases in the OT!–see context of verse 5), who already believe God exists: they can believe God exists, but they aren’t being trustful of God, and so not pleasing to Him, if they do not believe He seeks the good of those who are seeking Him. Thus the Hebraist begins this whole section in exhorting his readers who already believe in God’s existence! to have faith in God, i.e. to trust God: “Now faith is an assumption of what is being expected, a conviction concerning matters which are not being observed, for in this the elders were testified to.” (11:1, after which he runs through a list of archetypal Jewish examples, Enoch coming in at vv.5-6.)
The whole context is about Christians (and Jews) trusting in God–and specifically trusting in God’s salvation through the Messiah–even if we haven’t seen the fulfillment of God’s salvation yet. If we don’t trust God to save us, what the hell are we doing believing in God at all?! But “In faith these all died, not being paid with the promises, but perceiving them ahead and saluting them, and avowing that they are strangers and expatriates on the earth” (v.13) “Yet these all [after a second list of Biblical heroes and heroines], being testified to through faith, are not repaid with the promise of God concerning us–looking forward to any better–that apart from us, they may not be perfected.” (v.40)
So the Hebraist isn’t talking there about whether those who, at this time, cannot believe God exists, can please God; but about what pleases God among people who do believe God exists: namely that we trust God to save us, even if we aren’t being fully requited by God yet.
I can’t agree with you, it says “anyone who comes to him must believe that he exists”. Biblical authors need not only make statements limited to the context that they are speaking it (they can utter absolutes that jump out of the immediate context).