Presumption and Burden of Proof
Firearms instructors sometimes say that every gun is loaded. That is plainly false as it stands, but a wise saying nonetheless if interpreted to mean: every gun is to be presumed loaded until proven unloaded. Presumptions are procedural rules. To presume every gun to be loaded is to adopt a procedural rule to treat every gun as if it is loaded regardless of how antecedently likely it is that it is loaded. Suppose the likelihood is near zero: I examined the gun carefully an hour ago and I found it to be unloaded. Nevertheless, the presumption that it is loaded remains in force. I continue to behave as if it is loaded. For example, I don't point the gun at anything unless I want to destroy it.
I conclude that to presume that p is not to assert that p is true, nor to assert that p is probably true, nor to assume that p is true, but to decide to act as if p is true. A presumption, then, is not a proposition, although it embeds one. A presumption is something like a decision. More precisely, a presumption is the accusative of an act of presuming, an accusative that is not itself a proposition, but embeds one.
A presumption is not like a belief in the following important respect. To presume that a gun is loaded or that a man is innocent is not to believe that it is or that he is. To believe that p is to believe that p is true. But to presume that p is not to presume that p is true; it is to act as if p is true without either accepting or rejecting p. To presume that Jones is innocent until proven guilty is not to believe that he is innocent until proven guilty; it is to suspend judgment as to guilt or innocence until sufficient evidence is presented by the prosecution to warrant a verdict one way or the other. When I presume that p, I take no stand as to the truth-value of p -- I neither accept nor reject p -- what I do is decide to act as if p is true.
Presumptions must be defeasible. (I suspect that an indefeasible presumption is no presumption at all.) The presumption of being loaded is defeated in a particular case by carefully examining the gun and showing that it is unloaded. So while a presumption is not a proposition, it embeds a proposition that can be shown to be false. Defeasible presumption and burden-of-proof are correlative notions. (They are like rights and duties in this respect but also in that both are normative notions.) In a court of law, for example, if the accused enjoys a presumption of innocence, as he does in the Anglosphere, then the accuser bears a burden of proof, a burden which, if properly discharged, defeats the presumption.
Appeal to Ignorance?
So if person A claims to person B that a certain gun is unloaded, the burden of proof is on A to show that it is unloaded; person B does not bear the burden of proving that it is loaded. It is not just that he bears a lesser burden'; he bears no burden. Indeed it seems that B would be within his epistemic rights were he to claim that his ignorance of whether or not the gun is loaded is good evidence of its being loaded. But this is an appeal to ignorance. It has not been shown that the gun is unloaded; ergo, the gun is loaded.
It has not been shown that ~p; therefore p gives us the form of the ad ignorantiam 'fallacy.' Construed as a deductive argument, it is clearly invalid. Construed as an inductive argument, it will be in many cases weak. For example, suppose the gun is straight from the manufacturer and right out of the box. Then the probability of its being loaded is very low, and the argument: This gun out of the box has not been shown to be unloaded; ergo, this gun is loaded is very weak.
Nevertheless, safety considerations dictate a defeasible presumption in favor of every gun's being loaded, whether out of the box or not, a presumption that places the onus probandi on the one who maintains the opposite. So one might conclude that the appeal to ignorance in this case is reasonable even though the argument is deductively invalid and inductively weak.
The situation is similar to that in a court of law. The defendant is presumed innocent until proven guilty, so the burden of proof rests on either the state in a criminal proceeding, or on the plaintiff in a civil trial. In a criminal case the probative bar is set very high: the accused has to be shown guilty beyond a reasonable doubt. Here too there seems to be a legitimate appeal to ignorance: if it has not been shown that the defendant is guilty beyond a reasonable doubt, the conclusion to be drawn is that he is not guilty.
We will have to examine this more carefully in a separate post.
There are 'safety' considerations in both the gun example and the law example. It is because we want to be on the safe side -- and not get shot -- that we presume every gun to be loaded. "Better that a hundred guns be unnecessarily examined than that one sentient being be accidentally shot."
And it is because we want to be on the safe side -- and not sentence an innocent person -- that we presume the accused to be innocent until proven guilty. "Better that a hundred guilty people go free than that one innocent person be wrongly convicted."
But now what about God? Don't safety considerations apply here as well? If God exists, then our ultimate happiness depends on getting into right relation with him. So why can't one make a legitimate appeal to ignorance here? Now of course from the fact that no one has proven that God does not exist, it does not follow that God exists. That is an invalid deductive argument. That would be a truly fallacious instance of ad ignorantiam. But it is also invalid to infer than a gun is loaded because it hasn't been proven to be unloaded, or that a man is innocent because he hasn't been proven to be guilty. It just doesn't follow in any of these cases. And yet we reasonably consider the gun loaded and we reasonably find the accused to be innocent. And so why can't we reasonably presume God to exist on the basis of the fact that he hasn't been shown not to exist? If the burden of proof rests on the one who claims that gun is unloaded, why doesn't the burden of proof rest on the one who claims that God is nonexistent? We don't want to get shot, but we also don't want to lose our ultimate beatitude -- if ultimate beatitude there be.
You can't say that that the burden of proof rests on the theist because he is making a positive claim; for there are positive claims that need no proof. And you can't say that the burden of proof rests on the theist because he is making an existential claim; for there are existential claims that need no proof. If you claim that extraterrestrial intelligent beings exist, then the burden is on you. But if you claim that there are Saguaro cacti in Arizona, then the burden of proof is not on you but on the one who denies it. Nor can you say that the burden rests on the theist because he is controverting the widely-accepted; the consensus gentium is that God exists.
Earlier I argued that we shouldn't bring BOP considerations into the God discussion at all. But if we do, why doesn't the BOP rest on the atheist?
Massimo Pigliucci thinks that if one understands who bears the burden of proof in a trial, then one ought to see right away that the burden of proof rests on the theist. For, "the burden of proof is always on the party making a positive claim, not on the one making a negative one." This strikes me as confused. It is true that the party making a complaint or bringing a charge is making a positive claim, but this is not the reason why the BOP rests on the accuser. It rests on the accuser because of the presumption of innocence that the accused enjoys. The BOP rests on the accuser not because his claim is positive but because of the procedural rule enshrined in our system of law according to which one is presumed innocent until proven guilty.
It is not true that the BOP is always on the one who makes a positive claim. 'That hillside is studded with Saguaro cacti' said to my hiking companion needs no proof. I shoulder no probative burden when I make a commonplace observation such as that. Therefore, the following is an unsound argument:
Everyone who make a positive claim bears a BOP.
The theist makes a positive claim.
The theist bears the BOP in his debate with the atheist.
I argued above that if BOP considerations are relevant to the God debate, then the BOP is on the atheist. To appreciate the argument I gave, you have to realize that the God question is not merely theoretical. It is a practical question. In that respect it is like the gun safety and court room cases. My interest in whether or not a particular firearm is loaded or unloaded is not merely theoretical, or I should say, not at all theoretical. It is a practical interest in maintaining the health and physical integrity of myself and the people around me. Similarly with the law. If you are accused of homicide you are in deep trouble and face the loss of your liberty or your life. Arguably, the God question is in the same boat.
So I invite you to accept one or the other of the following conclusions. The BOP is borne by the atheist. BOP considerations should be kept out of the theist-atheist debate altogether.