Burden of proof
Burden of proof is the position, in argumentation theory, that the individual making a claim that something is true is required to support the claim with evidence or sound argument sufficient to warrant acceptance of the claim by the other party. If the claimant cannot provide sufficient evidence, the other party is allowed to disregard the claim without having to disprove it.
The primary reason why this is important is that the person who is making a claim tends to be the one who has access to the information and evidence. That person is thus the one in the best position to prove it, not the person who's just hearing about it.
While each individual is free to set their own standards of evidence, there are rules and accepted conventions which determine the evidentiary standards in courts of law, formal debates and other settings.
Some familiar examples:
- In the United States legal system, the burden of proof in most criminal trials is on the prosecution (claimant) to prove to a judge or jury that the defendant is guilty (the claim) beyond a reasonable doubt, because there is a presumption of innocence (thus presuming the claim to be false) going into the proceedings.
- Again in the United States, in most civil trials the burden of proof is on the plaintiff (claimant) merely to "tip the scales" in their favor, so that their claim is "more likely true than not" (also known as preponderance of the evidence or balance of probabilities). In this case, there is much more "symmetry" between the two sides of the case, and yet in the unlikely case of a "tie" — complete parity between the two cases presented — judgment must be in favor of the defendant.
Other legal burdens of proof include air of reality, probable cause and clear and convincing evidence. Other non-legal notions of burden of proof include benefit of the doubt and tie goes to the runner.
Another reason for the burden of proof being on the claimant is that such claims are propositions. Propositions in and of themselves present models of something. For example the proposition "Earth is a sphere" is presenting a model of Earth, in this case Earth being a sphere. For a proposition to be true two conditions must be met: the proposition is comprehensive, the model must be accurate. For humans to even be able to tell wether or not a proposition is true or false the proposition must be comprehensible. This means that we can comprehend the model. A model of a mind without a brain or similar physical system is not comprehensive nor is a god outside of time or space. Since we cannot comprehend such ideas, they cannot be proven nor disproven. Next the model must be accurate. Humans evaluate the accuracy of models empirically through evidence. Evidence and the analysis thereof is the only way for humans to know wether or not a model is accurate. The one who presents the model is in the best position to provide such evidence and the model is their proposal. Thus they have the burden of proof.
There is also a reason from practicality. It is much more practical for example to be agnostic towards all religions until the said religions meet their burdens of proof rather than try and disprove over 30,000 different religions.
In addition, just as each person is responsible for their actions, each person is also responsible for their claims. Such responsibility includes not only explaining the claims but also proving the claims. In a market place of ideas, accepting the claim can be viewed as a bargain: the claimant's end of the bargain is to prove the claim and the audience's end of the bargain is to accept the claim if and only if the claimant has upheld their end of the bargain.
A consequentialist reason is as follows, and is related to the market place reason mentioned above. If we accept one claim from a person on faith, why not accept everyone else's claims on faith? If we only accept claims from the first person in question, we are being biased, unfair, and committing the fallacy of special pleading. If we accept all claims on faith, in other words we do not demand evidence for any claims and anyone can just make up any claim, then there is no point in discussing anything for the truth. What would be the point of, lets say, a trial if we can just convict a defendant without demanding evidence from the prosecution because the prosecution made their accusation on faith? This leads us to a contradictory situation: we would have to accept both claims on faith if they were made: the defendant is guilty, the defendant is not guilty. The defendant cannot both be guilty and not guilty, the defendant is one or the other. Therefore if we accept faith as a substitute for the burden of proof, we will either commit a biased case of special pleading or we will run into contradictions. However if we require each claimant to meet their burden of proof, both of these problems are avoided. Thus the burden of proof is the best way of evaluating claims.
When asked to support the claim that a god exists, it's not unusual for an apologist to respond with "You can't prove God doesn't exist", or similar statements. Essentially, this is an attempt to shift the burden of proof (a logical fallacy).
A rephrasing of "I believe that god exists" into "I don't believe that god does not exist" is also an attempt to dodge the burden of proof - the proposed equivocation seeks to convert a claim acceptance to a claim rejection, but the two are not logically equivalent. "I don't believe that god does not exist" can be (and often is) a position held by atheists, and says nothing about how the person stands on the claim "god exists".