In the discussion between believers and non-believers, who bears the burden of proof? Who must present evidence, and who gets to decide whether the evidence is persuasive? The conventional wisdom is that the person affirming a belief must present evidence sufficient to move the one who denies or doubts the belief in question. Doubters do not need to make arguments for their doubt. And the doubter decides the question. Clearly, this presumption gives the doubter and denier an almost insurmountable advantage in discussions with believers. Does the believer really bear the burden of proof?
Let’s begin with logic. Are propositions that affirm something inherently less likely to be true than propositions that deny something? Or to put it another way, is it inherently easier to know the truth of the general proposition “A” than the truth of general proposition “not-A”? Apart from knowing what is being affirmed and denied in the real world by these propositions, I can’t see any reason for preferring “not-A” to “A”. In either case, one would need to survey the logical or existential space where the referent of “A” would reside if “A” were true. The assertion “A” finds the referent of “A” present in that space, and the assertion “not-A” finds the referent of “A” absent. The task is the same in both cases.
What about real world affirmations and denials? Is there something inherent in the real world that makes doubt and denial always the more rational option than affirmation and belief? The answer is no. Everyone would agree that someone faced with overwhelming evidence in favor of an affirmation would be acting less rationally to deny that belief than to affirm it. For example, suppose I deny that my child smokes marijuana even when confronted with a video of my child actually smoking marijuana. Clearly, I would not be acting rationally in my denial. I am allowing wishes and prejudices rather than reason to determine my beliefs. Hence whether one believes or doubts and denies is determined by more than the evidence presented on behalf of belief. It is also determined by one’s beliefs about other things, one’s prejudices, and one’s values. In other words, the amount of evidence required to persuade people is determined by the entire situation in which the argument takes place.
Consider the rhetorical rules in a court of law. In a criminal case, the prosecution always bears the greater burden of proof and must convince 12 people “beyond a reasonable doubt” of the defendant’s guilt. The defense need only create reasonable doubt in the minds of the jurors. Why lay this heavy burden on those affirming the proposition, “Defendant X murdered victim Y.” Are defendants always more likely to be innocent than guilty? No, that is not the reason for the burden. The reason is that our legal system presupposes that it is morally superior and socially more expedient to let a guilty person go free than to convict an innocent one. So, the side that must bear the greater burden of proof in a court of law is determined by the special situation that applies in that setting.
Someone may make the following objection to what I have said so far: to move from not believing to believing a proposition (for example, God exists.) requires evidence, but doubting or denying a proposition requires no evidence. But this is not true. You need a reason to doubt an affirmation. After all, doubting is an action. We are compelled to doubt or deny an affirmation when it conflicts with other beliefs, values, wishes, or prejudices we possess. If you doubt or deny that God exists, you do so because you sense the conflict between the proposition “God exists” and your other beliefs and values. You may doubt or deny God because you believe that “the physical world is all there is” or that “human freedom is not compatible with God’s existence.”
But this means that the rationality of your doubt and denial of God depends on the truth of your other beliefs and values, which themselves must be supported by evidence. The doubter and denier get no exemption from the need for evidence. Every argument between a believer and a non-believer always involves a confrontation between two systems of mutually supporting beliefs. Both parties affirm and both deny certain beliefs. There is no such thing as pure doubt or pure denial. To claim that one merely doubts and denies but does not affirm is to deploy a rhetorical trick. We should not fall for it.
I conclude that in the discussion about the truth of Christianity there are no general rules for who bears the greater burden of proof. There are no general rules for how much evidence is enough or what type of evidence counts in favor of Christian belief. And there is no objective third party qualified to declare when the burden has been met. The rhetorical situation in which the discussion takes place determines all these issues. Different people demand different levels and types of evidence and are moved by different arguments. In a particular phase of the discussion believers may need to present evidence for belief, but in a different phase non-believers will need to present evidence for their supporting beliefs, the beliefs that compel them to doubt and deny.
It’s as true in the argument between belief and non-belief as it is in the economic sphere: there is no free lunch. There is not even a subsidized lunch.