Do Other Religions Show that Christian Belief is Unreliable?

A popular objection to Christian belief comes from religious diversity. The objection goes something like this: Christianity is not the only world religion. Many other religions–Judaism, Mormonism, Islam, Hinduism, etc.–cite their own religious experience in support of their beliefs. But they all can’t be true. The mechanism that produces religious belief is therefore unreliable; it produces all sorts of false beliefs (even assuming one of them is true). It follows that religious belief can’t be trusted [1].

What are we to make of this objection?

Arguments & Evidence

A very natural response, and one that Christian apologists often give, is to provide arguments and evidence for the unique truth of Christianity. The reason that Christianity is justified, so they say, is because we have sufficient reason to think that it’s true and subsequent reason to think other religions are false. Christian thinkers like Tim McGrew, Richard Swinburne, Calum Miller, and many others defend something like this. Christian belief is justified in the same way that belief in atomic theory is justified: through good arguments and evidence.

Skeptics and Freethinkers are likely to object at this point that Christianity is still unjustified because the arguments in favor of Christianity are weak. That’s false, but notice the objection has shifted. Instead of being an argument from religious diversity, the objection is now that the arguments in favor of Christianity are bad. That’s a very different argument.

A Further Worry

A worry that might arise at this point is that most Christians do not believe in Christianity by way of argument and evidence. So, even if we grant that someone like Tim McGrew is justified in his belief, the vast majority of Christians are unjustified.

One response is to simply bite the bullet and admit that most Christians are not justified, epistemically speaking, in their belief. The only thing that would follow from this is that these Christians aren’t fulfilling their epistemic duties; it wouldn’t follow they aren’t saved or that they aren’t real Christians. Philosophers like Kierkegaard, Wittgenstein, and Pascal would openly embrace this form of epistemic rebellion.

Phenomenal Conservatism

A second response is to say that, actually, most Christians aren’t familiar with the objection from religious diversity–they don’t know it, haven’t heard of it, haven’t thought about it–and hence don’t have a defeater for their belief. Thus, most Christians enjoy at least some justification. This follows from a popular epistemic principle called phenomenal conservatism (PC). Here’s what PC says:

If it seems to S that P, then, in the absence of defeaters, S thereby has at least some justification for believing that P.

The absence of defeaters clause is essential to this response. Many Christians that believe in Christianity apart from argument and evidence haven’t heard of this objection from religious diversity. One might argue they should have heard of it, but that’s a separate worry. Given PC (and assuming an absence of other defeaters), they have at least some justification believing in what seems to them to be the case.

Of course the question is now: But what about those that (i) believe in Christianity not on the basis of argument and evidence and (ii) have heard the objection from religious diversity? Doesn’t it follow that they are unjustified? I will argue that the answer to this question depends on whether Christianity is true. If Christianity is true, then Christian belief is probably reliable, but if Christianity is false, then it probably isn’t reliable (note that this is essentially identical to the thesis of Reformed Epistemology).

Before doing that, let’s get clear on the Christian picture of justification and warrant.


On Christianity, humans have fallen into sin and require redemption. The mechanism that was originally designed to engender belief in God is now damaged and in need of repair. Fortunately, God sent a remedy into the world through His divine Son, Jesus Christ.

Now, God could have conveyed this message of salvation a million different ways but this is how He did it according to the Christian story. First, He supervised and divinely inspired the collection of writings we call the Bible. Second, He sent us the Holy Spirit. Third, through the inner witness of the Holy Spirit, we come to see that the central Christian claims are true.

The Holy Spirit restores or repairs the damages of sin. It is by the work of the Holy Spirit that Christians come to believe in the great truths of the Gospel. Christian belief, therefore, is not brought about by way of any natural process; it involves the work of the Holy Spirit.

Howard’s Hosts

With that concept in mind, consider an analogy I’ve dubbed Howard’s Hosts. It’s loosely based on the HBO series “West World.”

Howard, a mad scientist, has decided to increase his productivity by designing a race of conscious cyborgs, or “hosts.” Unfortunately, the hosts suffer a peculiar cognitive defect. The mechanism responsible for producing beliefs about their creator is broken. Some of the hosts believe that Howard’s name is George, others believe his name is Patrick, and so on. It’s natural to think the host’s ‘naming mechanism’ is unreliable. Now, suppose Howard locates the problem and installs a firmware update into the cyborgs. He designs the update such that it can be rejected by the hosts. And as it turns out, 70% of the hosts end up rejecting it. With this in mind, it appears that, despite the large percentage that have rejected the update, the remaining 30% of hosts that accepted the update have had their naming mechanism repaired. Their naming mechanism is no longer unreliable.

Notice the two-stage process: Stage One is the ‘Defect’ stage. Here we learn that some cognitive faculty or mechanism is broken. The second stage is ‘Repair.’ Howard introduces a firmware update that can either be rejected or accepted. For those that accept the update, their beliefs about Howard are reliable.

Full Circle

Here’s how the argument works: For any host that accepts the update, their naming mechanism is no longer unreliable. And obviously, for any host that does not accept the update, their naming mechanism remains damaged. Similarly, if Christianity is true, then there is such a person as the Holy Spirit that is constantly repairing the damages of sin. However, if Christianity is not true, then there is no such person, nor is there any sin.

The upshot is that the objection from religious diversity constitutes a defeater for Christian belief only if Christianity is false. If Christianity is true, then Christian belief is probably reliable (through the inner witness of the Holy Spirit). So one can’t say that Christian belief in particular is unreliable unless one is prepared to argue that Christianity is false.


In summary, many Christians offer arguments and evidence for the unique truth of Christianity. That’s the first response. The second response is to say that a defeater from religious diversity affects only a tiny number of Christians and so many of them, given PC, enjoy at least some amount of justification. The third and last response is to say that this objection only constitutes a defeater for Christian belief if Christianity is false. In other words, the epistemological question isn’t separate from the metaphysical question. The person that seeks to argue that Christian belief is either unreliable or unjustified must, in reality, argue that Christianity is false.

To the skeptic that seeks to establish that: God speed.


[1] For anyone that would like to read an academic treatment of this argument, see this recent paper by McNabb and Baldwin.

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MaunujimboCameron BertuzziJohn Recent comment authors
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It follows that Christians must prove other religions false before claiming theirs is true.


Thank you, Cameron, for an excellent introduction! Something to mull over.