The burden of proof (“onus probandi” in Latin) is the obligation to provide sufficient supporting evidence for claims that you make. For example, if a politician claims that a new policy will lead to a positive outcome, then the politician has a burden of proof with regard to this claim, meaning that they need to provide evidence that supports it.
The burden of proof is an important guiding principle, which is used to help people conduct discussions and resolve disputes, so it’s highly beneficial to understand it. As such, in the following article you will learn more about the burden of proof, and see how you can account for it in practice, including in cases where people display the burden of proof fallacy by attempting to evade their burden of proof.
Examples of the burden of proof
An example of the burden of proof is that if someone claims that their solution to some problem is better than the alternatives, then they need to provide evidence that shows that this is indeed the case.
Another example of the burden of proof is that if someone in a philosophical debate claims that the opposing team used fallacious reasoning, then the person who made this claim needs to prove it with appropriate evidence.
In addition, the following are other examples of situations where the burden of proof plays a role:
- If a scientist claims that their theory can explain a certain natural phenomenon, then the burden of proof means that they need to provide evidence that supports this claim.
- If a person sues someone for causing them financial losses, then the burden of proof means that the person who is suing needs to prove in court that the other person is responsible for those losses.
- If a company claims that a medication that they developed is effective and safe, then the burden of proof means that they need to support this claim using clinical data.
Who has a burden of proof
An individual or group generally has a burden of proof with regard to any claims that they make, which means that they have to provide sufficient evidence in order to support those claims, either as part of their original argument, or in response to the claim being questioned.
When it comes to discussions, for example, this means that each side generally has a burden of proof with regard to their claims, and the other parties may invoke this burden by asking questions or providing counter-arguments. Accordingly, the burden of proof can shift between the discussants, meaning that different people are expected to provide supporting evidence at different stages of the discussion.
However, in practice, determining who has a burden of proof and when can be a complex and controversial issue. As one scholar notes:
“How do we tell generally in a given case which side has the burden of proof? How this is to be done depends on how much information there is in a given case and what kind of discussion is supposed to be taking place.
The normal default rule is that the party who makes a claim has the burden of proof to support that claim if the other party questions it. Thus, in many cases it might be a very simple matter to analyze an example with respect to burden of proof if the example is one where a claim has been made, that is some proposition has been put forward as an assertion, and those of us who are attempting to analyze or evaluate the argumentation in the example question the claim.
Other cases… are not so simple. There may be a lengthy chain of argument presented on both sides, for example in a case of argumentation put forward in legal trial or a forensic debate. In this kind of case we have to confront the problem of how the burden shifts back and forth during the entire sequence of argumentation as the parties on both sides take turns putting forward challenges and counterarguments.”
— From “Burden of proof, presumption and argumentation” (Walton, 2014)
Various approaches have been proposed when it comes to determining who has the burden of proof, and what kind of burden they have, at any given stage of an interaction.
One common solution is to rely on a third party, such as a judge in a legal trial, who can help guide the discussion and resolve disputes, often by relying on preexisting rules. Another solution is to conduct a meta-dialogue (or meta-discussion), where the individuals involved discuss their dialogue up to that point, including the arguments that they’ve made and their overall goals for the dialogue, in order to determine who has a burden of proof at this point.
Such solutions can be particularly important in cases where people refuse to acknowledge their burden of proof, for example by refusing to provide supporting evidence for their claims, or by refusing to retract their claims despite the lack of supporting evidence.
Overall, people have a burden of proof with regard to any claim that they make, so they must support it either when they present it or when it is questioned by others. However, determining who has the burden of proof can sometimes be difficult, which necessitates the use of solutions such as having a neutral third-party guide the discussion.
Types of statements
According to some views, there are three main types of statements, each of which involves a different burden of proof:
- An assertion carries a burden of proof. If you assert something (i.e., claim that something is true or false), then you have a burden of proof to demonstrate that this is indeed the case.
- A presumption carries a conditional burden of proof. If you presume something (i.e., ask someone to accept something as true or false unless they have objections), then you don’t necessarily have a burden of proof with regard to that presumption, unless your opponent questions it, at which point you must either prove your presumption or retract it.
- An assumption carries no burden of proof. If you assume something (i.e., treat a certain claim as true or false just for the sake of the argument, without committing to it actually being true or false), then you don’t need to prove it. However, this also means that an assumption can generally be dismissed without evidence, which can be an issue for arguments that rely on it.
Drawing a distinction between these types of statements can be beneficial in various situations. For example, if a discussion has gotten stuck because you and your partner disagree on some point, proposing a certain assumption could help the discussion move forward, even if you can’t prove the associated claim.
Note: the terms outlined here (assertion, presumption, and assumption) can have different meanings in different contexts. For instance, in the legal context, presumptions can be viewed as “default rules”, as in the case of the presumption of innocence, which denotes that a defendant is innocent until proven guilty.
Burden-of-proof tennis (also called burden tennis and the onus game) is a phenomenon where a discussion revolves primarily around disagreements regarding who has the burden of proof at any given moment.
One example of burden tennis is a debate where the two opposing teams keep arguing about which of them needs to provide evidence in support of their stance.
Another example of burden tennis appears in the following quote, which also demonstrates that burden tennis can appear in conjunction with other types of problematic rhetoric:
“Fodor is too wise to think his series of arguments can flat disprove the claims of the opposition, so time and again he resorts to claims about shifting the burden of proof, begging the question, outsmarting by embracing the conclusions of reductions, and other exploitations of the rules of the game.
The book is a tireless exercise of that philosopher’s pastime, burden-tennis. Burden, burden, who has the burden of proof now? Fodor mostly plays solitaire burden-tennis, against an imaginary opponent often personified as Granny or Aunty, which permits him to express the opposition view in terms that suit his rebuttal, without having to address the issue of whether this is a sympathetic rendering of any real opponent’s claims.
— From Daniel Dennett’s 1988 review of Jerry Fodor’s “Psychosemantics”
Burden tennis can be detrimental to discussions, for example when it shifts the discussion away from the original topic under consideration, and instead pushes it into an unproductive fight about who has the burden of proof.
According to dialogical foundationalism, certain propositions are privileged, which means that they only need to be supported or retracted in the face of what is perceived as a valid challenge with sufficient support. This is contrasted with dialogical egalitarianism, according to a person must either support or retract any claim that they make, if that claim is questioned.
For example, under dialogical foundationalism, a scientist may choose to not respond to criticisms of well-accepted scientific theories, unless those criticisms are properly supported by scientific evidence. This means, for instance, that a scientist might not respond to criticism such as “scientists are wrong, since the Earth is flat”, which contradicts the scientific consensus, unless the person who makes the criticism can provide sufficient evidence to support it. Conversely, under dialogical egalitarianism, the scientist would be expected to respond to this criticism or retract their claim even if it’s unsupported.
The concept of privileged propositions is controversial, as it is associated with various issues.
For example, one notable issue is the disagreements regarding what constitutes a privileged proposition. Some argue, for instance, that propositions are privileged if they are “common sense”, while others argue that propositions are privileged if they support “well-established” procedures or the “status quo”. However, not only is there disagreement regarding what criteria should be used to define privileged propositions, there is also disagreement regarding the assessment of these criteria, for example when it comes to determining what constitutes “common sense” or “status quo”.
In addition, claiming that a certain proposition is privileged may involve its own burden of proof. For example, if someone claims that the Earth not being flat is a privileged proposition, they may need to support this claim with evidence showing the scientific consensus on the topic.
Overall, the concept of dialogical foundationalism and of privileged propositions is controversial, as it involves many potential issues. This means that, depending on factors such as the goal for a discussion and the context in which a discussion occurs, dialogical egalitarianism may be more appropriate, and that even when dialogical foundationalism is accepted, it’s important to remember that there are many considerations regarding how it should be implemented, for example when it comes to determining what constitutes a privileged proposition.
Standard of proof
A standard of proof is the level of evidence that must be provided in order to successfully fulfill the burden of proof in a certain situation. For example, in the legal context, the expected standard of proof expected of the prosecution may be “beyond all reasonable doubt”, which generally means that they “must convince the jury that there is no other reasonable explanation that can come from the evidence presented at trial”.
Different circumstances call for different standards of proof (sometimes also referred to as types of burden of proof). For example, in the context of the U.S. legal system, common standards of proof include:
- Beyond a reasonable doubt, which generally means that “the prosecution must convince the jury that there is no other reasonable explanation that can come from the evidence presented at trial”.
- Clear and convincing evidence, which generally means that “the evidence is highly and substantially more likely to be true than untrue”.
- Preponderance of the evidence, which generally means that “there is a greater than 50% chance that the claim is true”.
Various other standards of proof may also be used in the legal context, including, for example, some evidence, some credible evidence, substantial evidence, reasonable belief, reasonable suspicion, reasonable indications, and probable cause.
Furthermore, other standards of proof may be used in different contexts, or the same standards may be used but with different definitions.
What constitutes a reasonable standard of proof depends on various factors, such as the context in which a claim is being made. This means, for example, that the standard of proof in a casual conversation will likely be different than the standard of proof in a scientific paper. Moreover, the standard of proof may also, for example, vary between scientific papers in different domains, and it may even vary between different claims within the same paper.
Finally, note that it’s possible to associate different standards of proof with different levels of certainty, based on various criteria. For example, one paper proposed a 0-10 scale of certainty, where level 9, for instance, corresponds to the “beyond a reasonable doubt” standard of proof, and has a probability of >99%, indicating that something is “virtually certain”, in the sense that it has been “rigorously proven” as “critical experiment(s) [gave] a clear result”. Similarly, on this scale, level 6 corresponds to the “substantial and credible evidence” standard, and has a 67–80% probability, indicating that something is “probable”, in the sense that “evidence points in this direction, but [it is] not fully proven”.
Note: when it comes to the standard of proof, one related concept is the Sagan standard, which suggests that “extraordinary claims require extraordinary evidence” (a concept abbreviated as ECREE). This signifies that the more unlikely a certain claim is, given existing evidence on the subject, the greater the standard of proof that is expected of it.
The burden of proof fallacy
What is the burden of proof fallacy
The burden of proof fallacy is a logical fallacy that occurs when someone tries to evade their burden of proof, by denying it, pretending to have fulfilled it, or shifting it to someone else.
For example, if a politician is asked to justify a policy that they’re promoting, they may use the burden of proof fallacy by saying that they don’t have to justify the policy, or by saying that someone else should explain why the policy shouldn’t be implemented.
The burden of proof fallacy can involve several patterns of behaviors, all of which revolve around evading one’s burden of proof. The main such patterns of behavior are the following:
- Denying the need to prove a claim.
- Pretending that to have already proven the claim, without actually having done so.
- Shifting the burden of proof to others, by stating that they should disprove the original claim.
- Shifting the burden of proof to others, by stating that they should prove their own stance, while ignoring the burden of proof for the original claim.
These different forms of the burden of proof fallacy can themselves be implemented in various ways and combinations. For example, someone shifting the burden of proof to someone else might also explicitly deny their own burden of proof, or they might avoid mentioning their own burden of proof entirely.
Examples of the burden of proof fallacy
One example of the burden of proof fallacy is someone who claims that ghosts exists, but doesn’t prove this, and instead shifts the burden of proof to others, by stating that anyone who disagrees should prove ghosts don’t exist.
Similarly, another example of the burden of proof fallacy, this time in the context of marketing, appears in the following dialogue:
Marketer: Our new diet pills are guaranteed to help you lose weight.
Interviewer: Are they safe though?
Marketer: Do you have any evidence to suggest that they’re not?
Here, the marketer evades their burden of proof by shifting it to the interviewer, so that instead of the marketer proving that the pills are safe, the interviewer is asked to prove that they aren’t.
The two examples above illustrate a common way in which people engage in the burden of proof fallacy (referred to in this context as the argument from ignorance or argumentum ad ignorantiam), where it is suggested that if something hasn’t been proven to be false, then it must be true (and vice versa). Such arguments generally have the following basic structures:
Proponent: I assert X.
Respondent: Prove it.
Proponent: You disprove it.
Proponent: We should do X.
Proponent: Why not?
One study provides a real-life example of this kind of burden of proof fallacy in politics:
Sometimes this back-and-forth process leads to a kind of situation called the ad ignorantiam ‘tug of war’…
In a debate in the Canadian House of Commons, the issue was Opposition concern that the embargo on the export of Canadian uranium ‘for non-peaceful purposes’ was not being respected.
An opposition minister demanded that the Secretary of State for External Affairs prove that the treaty was being respected, after he had claimed that, as far as he knew, on the information that was available, it was being respected.
The opposition minister asked, “What is your proof?”…
The Secretary of State replied, “I have looked for any weakness in the treaty, and I have found none.” He told the Opposition not to be so secretive, “Come forward with your allegations so that we can find out whether they are true or false”…
The reply was, “Do a proper investigation.”
In this case, each side tried to shift the burden of proof back to the other side, in a typical ad ignorantiam tug of war. The problem, in such a case, is to determine on which side the burden of proof should rightly lie in the debate. In cases, where it has not been decided, an ad ignorantiam argument can go back in forth in this fashion through many moves.
— From “Rules for Reasoning from Knowledge and Lack of Knowledge” (Walton, 2006)
Furthermore, people who use the burden of proof fallacy in this manner often make claims that are not falsifiable, meaning that they can’t actually be disproven by evidence. This issue is illustrated in the concept of Russell’s teapot, which was proposed by philosopher Bertrand Russell:
“Many orthodox people speak as though it were the business of sceptics to disprove received dogmas rather than of dogmatists to prove them. This is, of course, a mistake.
If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense.”
— From “Is There a God?” (Bertrand Russell, 1952), as cited in “The Collected Papers of Bertrand Russell”, Volume 11 (1997)
In addition, the following is another example of the burden of proof fallacy, with a different structure:
Alex: Vaccines are bad for you.
Bob: Really? Where’s the proof of that?
Alex: I read it on a website.
In this example, Alex tries to evade his burden of proof by attributing his claim to a secondary source, without providing meaningful supporting evidence himself.
This form of the burden of proof evasion is sometimes combined with vague and ambiguous language, often through attribution of the claim to an unclear or anonymous source, as in the following example:
Alex: They say that vaccines are bad for you.
This example also demonstrates how attribution to a secondary source can be combined with a denial of commitment, where a speaker attributes the claim that they’re making to someone else, without committing to it themself. For example:
Alex: Jenny says that vaccines are bad for you.
Bob: Is there any empirical proof that supports this?
Alex: I’m just telling you what Jenny says.
This type of argument is not necessarily fallacious, but can be an example of the burden of proof fallacy in cases where people use it to indirectly express support for a certain stance, while evading the associated burden of proof.
Finally, the following is an example of the burden of proof fallacy, where a person simply denies their burden of proof:
Proponent: We should do X.
Proponent: I don’t have to explain my reasoning to you.
However, note that, as with many other examples of this fallacy, the context matters, as the above denial of the burden of proof may be reasonable in some cases but fallacious in others.
How to counter the burden of proof fallacy
There are several things that you can do to respond to someone’s attempt to evade their burden of proof:
- Point out that they’ve failed to fulfill their burden of proof. When doing this, you can explain what burden of proof they have and why they have it, based on the claims that they’ve made.
- Explain why they are the ones with the burden of proof. This is especially relevant in cases where they attempt to shift their burden of proof to someone else, for example by asking someone to disprove their claim, when they’re the ones who should be proving it.
- Ask them to fulfill their burden of proof or retract their claim. When doing this, you can also set conditions, such as that you won’t continue the discussion until they’ve fulfilled their burden of proof, while also explaining why it’s important that they do so.
- Call out the attempted evasion of the burden of proof. This can involve pointing out the specific way in which the person in question is evading their burden of proof, especially if they’re doing it by using other fallacious patterns of reasoning.
- Provide counter-proof. In some cases, it can be preferable to prove or disprove something yourself, rather than focus on someone else’s inability to fulfill their burden of proof, for example if the discussion won’t go anywhere otherwise. However, note that a failure to provide counter-proof on your part does not necessarily constitute evidence that can be used in order to support their stance, especially if their claims are phrased in a way that makes them inherently difficult or impossible to disprove.
- Focus on your own point. In some cases, it can be preferable to ignore the other person’s point, given their evasion of their burden of proof, and to instead focus on presenting your own point.
- Move on with the discussion. In some cases, it can be beneficial to simply drop a certain point and move on with the discussion. This might be the case, for example, when it’s clear that the current line of discussion isn’t going anywhere given the evasion of the burden of proof, but you believe that other parts of the discussion may be productive.
- Leave the discussion. In some cases, the best solution might be to simply leave a discussion entirely. This might be the case, for example, when it’s clear that the other person isn’t going to support any of their claims, and that consequently the discussion has no value for you.
The optimal way to respond to the burden of proof fallacy depends on various factors, such as the way the person is evading their burden of proof, the presence of an audience, the context in which the discussion is taking place, and your personal goals for the discussion.
Furthermore, you can sometimes modify your response as the discussion progresses. For example, if someone evades their burden of proof, you can start by pointing out their evasion, and then choose your next step based on their reaction to this.
In addition, there are several other things that could potentially help in cases where there are disputes about the burden of proof.
One such thing is to find a mutually agreed third-party, who can arbitrate the discussion and ensure that each party properly fulfills their burden of proof.
Another helpful thing is to agree, in advance, what is the goal of the discussion, which burden of proof each party has, and what is the expected standard of proof involved. This can also help when it comes to preventing other issues, such as one party disingenuously moving the goalposts when it comes to the standard of proof that they expect from others.
Finally, note that the burden of proof fallacy is sometimes used in conjunction with other logical fallacies and rhetorical techniques, such as equivocation, circumlocution, red herrings, and the Gish gallop. The use of these added fallacies can make it more difficult to identify the use of the burden of proof fallacy, and is also something that you might need to address directly in your response. For example, if someone uses a fallacious personal attack while shifting their burden of proof to someone else, you might need to address the attack at the same time as dealing with the attempted evasion of the burden of proof.
Note: when it comes to responding to the burden of proof fallacy, a related concept is Hitchens’s razor, which is the adage that “what can be asserted without evidence can also be dismissed without evidence”.
The burden of proof in law
“Legal factfinding, like most real life decision-making, involves decision under uncertainty. Consequently, the legal system has adopted a set of decision rules to instruct judges and jurors how to decide cases in the face of uncertainty. These rules are collectively known as the burden of proof.
They include the well-known requirement that all accusations against the defendant in criminal cases be proven ‘beyond a reasonable doubt.’ For defenses that an otherwise guilty defendant may raise, the rules often require proof by a ‘preponderance of the evidence’ or proof by ‘clear and convincing evidence.’ In civil litigation, the burden of proof tends to treat plaintiffs and defendants as equals, normally requiring each party to prove her allegations—the plaintiff’s cause of action and the defendant’s affirmative defenses—by a ‘preponderance of the evidence.’ For allegations of crime and fraud in civil cases, the proof burden is often set to ‘clear and convincing evidence’—a special proof requirement that also applies in proceedings that might deny a person certain civil rights, such as deportation, denaturalization, involuntary confinement to a mental institution, and removal of parental rights.”
— From “Evidence, Probability, and the Burden of Proof” (Stein & Allen, 2013). The original text contains several references as footnotes, which have been omitted here for brevity.
In addition to the types of burdens of proof outlined in the above quote, other types of burdens of proof may also play a role in legal proceedings, depending on the jurisdiction. For example, in some cases there is a distinction between the burden of production, which generally involves “A party’s obligation to come forward with sufficient evidence to support a particular proposition of fact”, and the burden of persuasion, which generally involves “The obligation of a party to introduce evidence that persuades the factfinder, to a requisite degree of belief, that a particular proposition of fact is true”.
Similarly, in some cases there may be a reverse burden of proof (also known as reverse burden or reverse onus), where a defendant in a criminal trial must prove their innocence, as contrasted with a “regular” burden, where the prosecution must prove the defendant’s guilt.
The history of the burden of proof
One paper describes the history of the burden of proof as follows:
From a historical point of view, the term burden of proof originates in classic Roman law in which these “burdens” (i.e., task; order; obligation) were used to present arguments in the name of onus probandi (cf. “burden of proof”). This term was specifically related to the fundamental, legally determined division of work and roles between the prosecutor and the counsel for the defense in legal proceedings: The onus probandi answered the procedural question which party should come when with evidence. Under classic Roman law the prosecutor had to start first in all cases and give an explanation of his charges; subsequently, he had to present arguments for his “case” (agenti incumbit probatio), after that the counsel for the defense had to argue his “counter case” in the so-called exceptio, then it was the prosecutor’s turn again with his replicatio, and so on…
In short, the burden of proof, in all cases, initially laid with the party that made an accusation. The basic assumption was expressed by the fundamental rule: Necessitas probandi incumbent ei qui dicit non ei qui negat (the obligation of proof rests with the person who makes the claim, not the one who denies the claim).
— From “The Opening Stage: The Obligation-to-Defend Rule (I)” (van Eemeren, Garssen, & Meuffels, 2009)
In addition, according to the Oxford English Dictionary, the term “burden of proof” was first used in English writing in 1593, in Richard Hooker’s “Of the lawes of ecclesiasticall politie: the fift booke” (published in 1597), which states “The burthen of prouing doth rest on them.”.
The term “onus probandi” appeared later in English writing, with the earlier use of it appearing in a 1722 article in The London Gazette, which states that “The Onus Probandi shall lie on the Exporter, Claimer, or Owner thereof.”.
Finally, note that the term “onus of truth” is sometimes used to refer to the burden of proof. This term first appeared in English writing in 1827, in John Joseph Powell’s “An essay upon the learning of devises”, which states that “The onus of proof would be on the complaining party..to shew reasons for his dissent.”.
Summary and conclusions
- The burden of proof (“onus probandi” in Latin) is the obligation to provide sufficient supporting evidence for claims that you make.
- For example, if someone claims that ghosts exist, then the burden of proof means that they need to provide evidence that supports this.
- The burden of proof fallacy is a logical fallacy that occurs when someone tries to evade their burden of proof, by denying it, pretending to have fulfilled it, or shifting it to someone else.
- People sometimes hide their evasion of the burden of proof in various ways, such as by denying personal commitment to the claim, shifting the responsibility for the claim to a secondary source, making claims that are unfalsifiable, or combining the burden of proof fallacy with other logical fallacies and rhetorical techniques.
- To respond to the burden of proof fallacy, you can point out the failure to fulfill the burden of proof, explain why the person in question has that burden, ask the person to fulfill their burden or retract their claim, call out the attempted evasion of the burden, provide counter-proof, focus on your own point, move on with the discussion, or leave the discussion entirely.