Of course, this is a loaded question. It assumes that universalism is a heresy. But how do we decide that? To engage this question seriously, we'd first need to wrestle with the concept of heresy itself. Olson does offer a brief definition of heresy in a parenthetical remark, saying that heresies are "theologically incorrect beliefs," but he doesn't consider the adequacy of this definition in the face of alternatives. A "theologically incorrect belief" is presumably a belief about God that doesn't correspond with the way God really is. If this is what a heresy is, then we'd expect--as Olson immediately concedes--that all Christians are heretical about something or other, and that heresy needn't be a very serious issue. The (laudable, I think) implication of this way of conceiving the matter is that the cry of heresy loses much of its force. Being a heretic ceases to be an eggregious matter, at least as such.
But the reason why this definition of heresy (and the contrary notion of orthodoxy) has these implications is because it makes the objective nature of reality the standard by which beliefs are judged heretical (or orthodox)--and it seems inevitable that each of us will, in our beliefs about ultimate reality, get some things wrong. But I think this way of understanding heresy has deeper implications that Olson (and other evangelical Christians) would be unhappy to accept. Consider: on this definition, if atheists are right about the nature of reality then all Christians of every stripe are heretical in all their theological beliefs, since all their theological beliefs would then be wrong.
Is this a possibility we should concede? Part of the trouble here is that the way Olson is actually using the term "heresy" doesn't seem to fit with this possibility. He is asking, in effect, what is orthodox and what is heretical from within a Christian context. His starting point is that Christianity, in some broad sense, is correct about the nature of reality, such that the truth of atheism isn't really on the table. More to the point, if atheism were correct this would imply that there is no meaningful framework within which it makes sense to distinguish between orthodox and heretical Christian beliefs.
Now I don't have any trouble with adopting such a presupposition for the purposes of pursuing a more circumscribed discussion: "What should Christians believe about x or y?" seems the sort of question that ought to be askable apart from being able to definitively establish that the fundamental nature of reality is theistic. But if we are asking about what Christians should believe without committing ourselves to first resolving the deep philosophical questions about ultimate reality, then our standard of orthodoxy, if you will, has got to be something other than the fundamental nature of reality.
But perhaps Olson (or if not Olson, then some more fundamentalistic Christian) would like to argue that we can settle basic metaphysical questions, such as wehether God exists, and then use these answers (which are presumably in line with Christian teaching) as a framework for establishing what is orthodox and what is heretical. But as someone who has engaged philosophically with the atheist challenges to theistic beliefs, I am pretty confident that we are not in an epistemic situation where we can say that we know that the atheist is wrong. While I find some arguments for God's existence more convincing than atheists do, this is in large measure because I have a different intuitive response to the foundational assumptions on which these arguments build. As I've argued in Is God a Delusion?, these assumptions are ones about which apparently reasonable people can and do disagree.
Since these assumptions are, furthermore, foundational in character as opposed to being deduced from evidence or arguments whose merits are uncontested, it strikes me as ad hoc and presumptuous to simply assert that those who seem otherwise reasonable but who don't share one's immediate confidence about these assumptions are therefore unreasonable. Better to say, I think, that reasonable people can and do see the world differently at the most basic level, because when it comes to the fundamental nature of reality our epistemic situation is inescapably ambiguous.
In fact, there are reasons to think that this epistemically ambuiguous situation is precisely what should be expected on a broadly Christian theistic understanding of fundamental reality. As John Hick and Simone Weil and others have suggested in various ways, our status as individual persons who exist in some measure apart from or other than God requires that the divine in some sense "withdraw," producing a "distance" between creature and creator. And as Hick notes, if God is omnipresent this distance cannot be a spatial one. "It must be an epistemic distance," Hick observes, "a distance in the cognitive dimension." The world in which we live, he argues, must be "religiously ambiguous, capable both of being seen as a purely natural phenomenon and of being seen as God's creation and experienced as mediating God's presence."
Now to get to this conclusion, one needs a certain picture of the divine, one where God cares so much about establishing and preserving the otherness of the creation that withdrawal behind a veil of mystery is called for despite the costs. It is not my intention here to defend this picture of God, but rather to point out that, in saying that the fundamental nature of reality is in some sense unknowable, one is not ruling out a theistic understanding of reality--since such epistemic ambiguity might be the very thing we would expect under certain theistic worldviews. If one is to embrace those theistic worldviews at all, the embrace would have to be rooted in something other than knowledge of its truth. To embrace such a theistic worldview with an attitude of certitude would amount to a kind of contradiction. It would amount to saying, "I am certain that there exists a God who, if He existed, would guarantee that no one could be legitimately certain that He existed."
This is not to say that the believer in such a God couldn't acquire reasons for confidence--but the confidence would come after the embrace, not before, and the confidence would have the character of an inner experiential assurance as opposed to public evidence that could be trotted out for the sake of convincing the skeptic. If there is something that is public, it's the effects of belief on the life and character of the believer; but such effects do not count as "proof" in the sense of considerations that compel the belief of reasonable people who are confronted with them.
This may seem like a major digression from my starting point, but it bears directly on Olson's definition of heresy as "theologically incorrect belief." To define heresy in this way is to set the fundamental nature of reality as the standard for distinguishing between heresy and orthodoxy. If the fundamental nature of reality is hidden from us in a basic way--as it would be under at least some plausible understandings of the divine nature--then this standard is essentially inaccessible. And a definition of heresy that asks us to distinguish beliefs according to an inaccessible standard is basically useless. To define heresy in this way is to do more than just mute the force of cries of heresy. It is to say that there is no point in talking about what is orthodox and heretical, since we have no way of determining which is which.
I'm pretty certain that Olson did not intend anything as radical (from an evangelical Christian perspective) as this. But I'm also pretty sure that the broad theistic perspective Olson embraces commits him (however unwittingly) to the view that our life situation is epistemically ambiguous in something like the manner Hick describes. And why do I say that? Because of Olson's reasons for rejecting universalism.
According to Olson, universalism can only be a matter of pious hope, not a matter of confident belief, because of the nature of human freedom. Here's how Olson puts it in his essay on universalism and heresy:
I would have to wonder how a God of love can enjoy love from creatures that is not given freely. Of course, someone might argue that, in the end, every creature will freely offer love to God and be saved (e.g., Moltmann). I would just call that optimism. There’s no way to believe that true other than a leap of optimistic hope.
More significant, however, are Oslon's thoughts from an earlier post on eternal damnation as something that results from how we use the gift of free will. Olson distinguishes between "true freedom"--which is possessed only by "one who is all that God intends for him or her to be"--and "free will," which is that power of choice by which we can "move toward or away from that real freedom." According to Olson, "God graciously extends to all the possibility of realizing true freedom IF we meet a certain condition–acknowledge our dependence on him and his grace and cease our own efforts to achieve it apart from God." Our capacity to meet or not meet this condition is, according to Olson, itself a gift of love. It affords us the capacity to determine our own fates without divine coercion.
On a basic level, this is very close to Hick. Hick believes that a God of love would give His creatures a measure of independence and freedom--a freedom that extends especially to the freedom "to open and close oneself to the dawning awareness of God". But Hick argues that the only way to secure such creaturely freedom is for God to create an "epistemic distance" which is the condition for the "cognitive freedom" to reject a theistic understanding of reality.
Why think that? It is clearly what Aquinas thought, and the reasoning isn't that difficult to grasp. On the broadly Christian picture of reality, God is the infinite objective good Who is the source of all finite goods. And as such, all creaturely goods flow from God. To be cut off from God is to be cut off from one's own good. To see and understand the truth about reality, given this portrait of what that reality is like, is to see and understand that nothing good can come from alienation from God. And to see and understand this is to see and understand that there is no reason--NONE--to reject God. All possible motives for such rejection are exposed as vacuous.
Furthermore, it is hard to credit the idea that creatures who are a product of this infinite and infinitely good God would be designed in such a way that they would gravitate towards this ultimate good when presented with it in an unclouded way. We are naturally ordered to union with God, Aquinas maintains, in such a way that when presented with an unclouded vision of the divine we cannot help but love and long for it. Aquinas therefore thought that no creature of God, made for union with God, could, once presented with an unambiguous vision of God, choose to reject God. The clear sight of the summum bonum would swamp all other desires and expose all false beliefs about the choice-worthiness of rejecting God.
If one rejected God under those circumstances, it would have to be because human free will is subject to some kind of bizarre randomness that could act against all a creature's converging motives, leading them to do what they neither want to do nor think there is any good reason to do. And Aquinas did not believe that free will operated in this perverse way. Indeed, if free will were nothing more than randomness at work in human choices, it would hardly be a gift of God. More like a curse. To be saved or damned by a flip of the coin is hardly better than being saved by divine "coercion."
All of this is developed at considerably greater length and depth by John and me in our forthcoming book, God's Final Victory. The upshot of it for present purposes is this: The freedom to reject God depends on God creating an epistemic distance between Himself and His creatures. If God is as Christianity describes Him, then we would need a space of inescapable uncertainty about what God is really like in order to be able to freely reject God.
In other words, if one wants to defend the doctrine of hell by appeal to creaturely freedom--as Olson does--one needs to suppose that the human condition is suited to free rejection of God. And there is strong reason to believe that our human condition is suited to such free rejection only if it is characterized by an inescapable degree of epistemic uncertainty about God. And in that case, if "heresy" and "orthodox" are defined in the manner that Olson proposes, it becomes very hard to make any meaningful pronouncements about what is heretical and orthodox.