When debating any issue, there is an implicit burden of proof on the person asserting a claim. An
argument from ignorance occurs when either a proposition is assumed to be true because it has not yet been proven false or a proposition is assumed to be false because it has not yet been proven true.
[1][2] This has the effect of shifting the burden of proof to the person criticizing the assertion, but is not
valid reasoning.
[3]
While certain kinds of arguments, such as logical
syllogisms, require
mathematical or strictly
logical proofs, the standard for evidence to meet the burden of proof is usually determined by context and community standards.
[4][5]
In public discourse[
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Burden of proof is also an important concept in the
public arena of ideas. Once participants in discourse establish common assumptions, the mechanism of burden of proof helps to ensure that all parties contribute productively, using relevant arguments.
[6][7][8][9]
Proving a negative[
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When the assertion to prove is a
negative claim, the burden takes the form of a negative proof,
proof of impossibility, or mere
evidence of absence. If this negative assertion is in response to a claim made by another party in a
debate, asserting the falsehood of the positive claim shifts the burden of proof from the party making the first claim to the one asserting its falsehood, as the position "I do not believe that X is true" is different to the explicit
denial "I believe that X is false".
[10]
Example[
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Matt Dillahunty gives the example of a large jar full of gumballs to illustrate the burden of proof.
[11][12] It is a fact of reality that the number of gumballs in the jar is either
even or odd, but the beliefs a person could hold are more complicated. We can choose to consider two claims about the situation, given as
The number of gumballs is even.
The number of gumballs is odd.
These two claims can be considered independently. For each claim, because of the
law of excluded middle, we are forced to either believe or not believe. Before we have any information about the number of gumballs, we have no means of distinguishing either of the two claims. All of the information we have applies to claim 1 in exactly the same way it applies to claim 2. Due to the
law of noncontradiction we cannot accept both of the two
mutually exclusive claims, so we must reject (or not believe) both. This is the default position, which represents the
null hypothesis. The justification for this position is only ever the lack of
evidence supporting a claim. Instead, the burden of proof, or the responsibility to provide evidence and reasoning, lies with those seeking to persuade someone holding the default position.
