As far as I know, the "fallacy of shifting the burden of proof" is to refuse to show any evidence for my position, demanding the opponent to show evidence against my position, and claiming victory if the opponent refuses or fails to do so. This is in distinction to a fair use of the burden of proof.

Imagine the following conversation:

Alice: Unicorns don't exist.

Bob: Unicorns exist, and I have some in my garage.

Alice: Then show me proof of their existence, or show me your garage.

Bob: No! You should show proof why unicorns cannot possibly exist! Aha, you cannot, so I win.

This is a clear and egregious case of Bob shifting the burden of proof.

However, consider the following.

Alice: I consider the statement S to be true.

Bob: No, S is false!

Alice: Here I list evidence A, B, C, and D which support the theory of S being true. If you still don't want to accept S, then you should show me why I'm wrong with these pieces of evidence.

Bob: Aha, you are shifting the burden of proof!

Is Alice here really fairly shifting the burden of proof or is she committing what Bennett considers a fallacy? She actually came up with evidence for her position, and offered to debate those pieces of evidence.

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    – Geoffrey Thomas
    Commented Jun 21 at 9:17
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    "This is a clear and egregious case of Bob shifting the burden of proof." no it is not. Alice made a claim first. It will be if you remove first line ("Alice: Unicorns don't exist.") from your example.
    – talex
    Commented Jun 21 at 12:54
  • As far as we can tell, it might be the case that S = "the Earth is flat", A = "Water is always level", B = "Water does not stick to a ball", C = "A fire 150,000,000 km away could not possibly heat the Earth surface", D = "NASA sounds like the Hebrew word for 'to delude'", and A,B,C,D are to some extent not 100% false in everyday experience if Alice does some goal post pushing. -- And still, B should be willing to expose the obvious problems with A,B,C,D (as well as give simple evidence for his own claim) Commented Jun 21 at 13:04
  • @talex. Indeed. It is however a good example of Alice shifting the burden of proof.
    – JBentley
    Commented Jun 21 at 16:21
  • In your first example, neither Bob nor Alice provide any supporting evidence. Only Bob then explicitly claims to be right based on Alice's non-evidence, but implicitly based on the dynamics of the conversation, Alice is almost certainly thinking that Bob is wrong because he provides no evidence to counter her claim. BOTH are engaging in shifting the burden of proof in that example. In the second example, Alice is not shifting the burden of proof, she has instead satisfied it.
    – Dcleve
    Commented Jun 21 at 20:32

6 Answers 6


The concept of a "burden of proof" is fundamentally misguided, because everyone has a duty to justify their beliefs. Whether you think A, or whether you think not-A, you need a reason! And it doesn't matter who brought up A in conversation most recently.

In a philosophical discussion, all participants should be motivated by a spirit of honest inquiry. Both participants should seek to share their views and justifications clearly and honestly, and also to learn the views and justifications of the other person without misunderstanding. Comfortably sitting back and refusing to think about the subject is never a legitimate option.

Alice: I consider the statement S to be true.

Bob: No, S is false!

Alice: Here I list evidence A, B, C, and D which support the theory of S being true. If you still don't want to accept S, then you should show me why I'm wrong with these pieces of evidence.

Bob: Aha, you are shifting the burden of proof!

Alice is being more reasonable here. She provided specific evidence for why she thinks as she does. By doing this she showed some honesty. Now she offers Bob an opportunity to share his own justifications and show honesty in return.

Bob is refusing to be honest. He claims to think not-S, but why does he think so? Bob is treating the discussion as a combat to be won or lost, with the attitude that he should give his "opponent" as little as possible about his views so they cannot refute him. Bob imagines that "winning" is coming out of the discussion being able to confidently continue to assert not-S, and perhaps also having humiliated or insulted Alice in some way - regardless of whether Alice has a case or not! This is fundamentally dishonest and also irrational, because a rational person should desire to believe whatever is better supported by evidence, not cling to their initial view at all costs.

If a person truly believes their view is rational and well-justified, then they would welcome all questions about it, not stonewall! They would be eager to share the details of their well-constructed viewpoint, knowing it could only help their case.

If Bob cannot be persuaded to abandon this behavior, he is breaking an implicit social contract with Alice. If I were Alice, I would not be interested in discussing anything with Bob.

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    “n a philosophical discussion, all participants should be motivated by a spirit of honest inquiry.” — This is a bit of a spherical cow in a vacuum. It’s a very useful ideal for some purposes, but inappropriate for others. The concept of “burden of proof” is useful exactly in situations where discutants have other motivations besides unlimited pure inquiry, whether adversarial (convert the heretic! convince the jury!) or co-operative (understand each other’s views to a reasonable extent, but sooner or later agree to disagree, and move on with your lives). Commented Jun 20 at 11:13
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    @PeterLeFanuLumsdaine You aren't going to rationally "convert the heretic" without listening to them, addressing their concerns, and explaining why they should see it your way; you have to be honest and interested in the heretic's perspective, and also have a stronger case than they do, which you can help them to see. To convert a heretic is very different and much friendlier than to condemn a heretic. If you condemn the heretic, they will be defensive, not persuaded. I didn't say the discussion needed to be unlimited; what you describe as "co-operative" is close to an ideal outcome.
    – causative
    Commented Jun 20 at 15:08
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    "Convincing a jury" is a different matter, and can certainly be done without a spirit of honest inquiry, if the jury does not have respect for that spirit. You can appeal to emotion, you can insult your opponent, you can attack strawmen of your opponent's position, you can refuse to acknowledge any valid points your opponent has, you can decline to answer any questions you don't have a good answer for, and all this may be convincing to the jury, if the jury is not made up of reasonable people, which most juries aren't. This is what politicians do, and what you usually see on social media.
    – causative
    Commented Jun 20 at 15:15
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    I call that mode of discourse the mode of "dominance," because the goal is to hurt and humiliate your opponent and make them back down by any means at your disposal. While useful for gaining clout in a social hierarchy, the mode of dominance is a societal problem, because "winning" has so little to do with who has the more well-justified case. So false views can propagate. It would be better for society - and for whichever participant has the better-justified case - if participants in public debates could agree beforehand on rules of honest inquiry.
    – causative
    Commented Jun 20 at 15:29
  • It's not clear to me how you inferred the mindset driving Bob's actions. It seems at least as likely to me that Bob instead thinks, for example, that the not-S belief is sacrosanct - that being expected to provide evidence for it is somehow offensive. Commented Jun 20 at 20:44

You ask:

Is Alice here really fairly shifting the burden of proof or is she committing what Bennett considers a fallacy? She actually came up with proof for her position, and offered to debate those pieces of evidence.

It depends on what you mean by "actually came up with proof", since different parties may differ on standards of evidence and proof and in wider questions of epistemology. This is why, for instance, in the US legal system, there are standards of evidence to guide in questions of whether or not someone actually meets the burden of proof. In the example you lifted from Bennett, you simply don't provide enough information on the question if A,B,C, and D meet the burden, even in the abstract. So, if it is as you claim, that the standard has been met, it is not the egregious case, and if it hasn't then it is.

Generally, shifting the burden of proof is about having to show one's claims. In the Toulmin method, for instance, claims are established usually in tandem with warrants and rebuttals. Warrants function as sub-arguments which function as the premise to the claims, and preemptive rebuttals function as sub-arguments against anticipated counterarguments. It is fair to say that by adducing evidential warrants, one is indeed shifting the burden of proof by establishing that the primary claim must be true if the premises brought about by the sub-arguments are true. Now, your opponent can no longer argue against the conclusion, but rather against the basis upon which it rests. This, of course, is a good thing.

In law, this idea is encapsulated by a quotation attributed to Sandburg:

“If the facts are against you, argue the law. If the law is against you, argue the facts. If the law and the facts are against you, pound the table and yell like hell”

Inference in all cases moves from premises to conclusions. If an argument is strong, then you have to attack the premises upon which it rests, and if an argument is well-buttressed by evidence, then the burden of proof shifts to the interlocutor in opposition of the conclusion in the form of attacking the evidence. Consider the trial of O.J. Simpson, who when confronted with a strong prosecutorial evidence, had a defense attorney smart enough to get the jury to witness the process of the Squeeze trying to put on the glove used by the murderer. He ostensibly failed struggling to get the glove on. In essence, the attack worked by demonstrating that the claims surrounding the evidence were not as they seem. In fact, that the evidence that seemed to support the prosecution's case actually vindicated the defense's case. (Of course, one has to wonder just how "cooperative" the Squeeze was when he "trying" to put the glove on. He escaped criminal penalty but later was found liable in a civil trial where the standards of evidence were less.)

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    The question as asked asks if a claimant has the burden of proof, adduces a strong evidential basis, have they shifted the proof back? The answer is yes. But the fallacy Bennett lists is the case where the claimant has the burden of proof, does NOT adduce strong evidence, and then demands the burden be shifted back. Of course, this hinges on whether the evidence is generally strong. Evidence might be very strong, or it might be prima facie, or it might be probative. The break down in fair argumentation happens when the two parties have different theories of evidence and epistemology...
    – J D
    Commented Jun 19 at 22:20
  • Thus, whether or not a fallacy is committed depends on the details. I took a brief look at your dust up with NotThatGuy, who is an otherwise, uh, passionate thinker, but there's too much to figure out what went on at a glance. If you tag me in the conversation and bring my attention to a specific portion of the exchange, I'd make a neutral ruling.
    – J D
    Commented Jun 19 at 22:22
  • Thank you for the offer of taking a look. I don't want to waste your time, so I'll try to first formulate a summary as short as possible, and will tag you if and when I do.
    – vsz
    Commented Jun 21 at 7:53
  • I don't know if the tagging worked. chat.stackexchange.com/transcript/message/65895530#65895530
    – vsz
    Commented Jul 2 at 21:51

Yes. A claimant of an unusual claim has the philosophical burden of proof, they cannot rationally demand others to invest effort.

This is not necessarily about heated debate, but just common sense.

The status quo, the current paradigm, whatever you want to call it, is typically the result of great and lengthy efforts of analyzing evidence. In debate, it can typically be used without further evidence as fact (even if it's always possible to be false). As an example, one can use the fact that earth is round in debate today without having to provide evidence yet again.

It also means that anyone making claims against the status quo will be dismissed rightfully until their evidence is strong enough. Such as if a claimant claims earth is flat, their evidence must be strong enough to consider all previous evidence and analysis was wrong.

It would be irrational if any time someone thought they had a new piece of evidence for some pseudoscience, that this pseudoscience now becomes acceptable fact until somebody else refutes it. The common position rationally remains the dominant one. This becomes more obvious whenever one compares all claims of all pseudosciences as an example. Typically claimants of one pseudoscience demand that their own arguments should be given more weight, but at they same time they also dismiss the other pseudosciences, not giving much attention to the evidence given by those other claimants.

This is why this site as an example has rules against pushing personal ideology over what is accepted philosophy. Just because some pseudosciences claim to have evidence of something, their positions are not to be taken as facts until philosophy, society, academia... have accepted that evidence as sufficient to change paradigms.

Extraordinary claims require extraordinary evidence.

Another real world example is Darwins Origin of species, which Darwin wrote and the did not publish for 20 years, knowing his evidence would not carry weight. Even though Darwin was right about evolution in principle, he rationally knew that his would be the burden of proof and he could not just expect others to go and investigate his evidence. He waited until other publications and discoveries made his claims less difficult to believe.


No. This is not shifting of the burden of proof. If you provide evidence for your beliefs and then ask for debate or investigation of evidence then it is called proper engagement of verification of proof.


Verum that for any proposition p that comes up in discourse, p must always be accompanied by justification. So if p = There are unicorns in the garage, Alice has to justify p. If ¬p = There are no unicorns in the garage, Bob too has to justify ¬p. To get to the point, any assertion should possess a supporting justification.

Shifting the burden of proof is a fallacy IFF the person (asserting p) demanding it believes that his opponent's failure to justify the negation (¬p) is a justification for p. It is not. I surmise it's a failure to understand basic logic and it appears to be closely associated with the perfectly valid argument form Disjunctive Syllogism. In a disjunctive syllogism, proving one of the disjuncts false does imply the truth of the other disjunct.

Note the distinction though. Proven false (the negation), which is logically valid for disjunctive syllogism vs. Failure to prove (the negation), which is logically invalid for shifting the burden of proof. Related/identical to argumentum ad ignorantiam (argument from ignorance), where the person assumes p true because it's unproven that p false.

If you furnish evidence for your position p then you've done your part. It is your opponent's turn to critique your argument. This is not shifting the burden of proof. You didn't claim that because your opponent couldn't prove the negation of your assertion that your assertion is now (miraculously) true.


If a person says "I believe X because I believe A, B, C, and D are true, and that the combination of A, B, C, and D proves X", then their conclusion would be unsound if any of A, B, C, or D could be false, or if all four of them could be true while X was false. If one's audience would e.g. accept that A, B, and D are true, but would dispute C, then any efforts spent trying to prove A, B, and D would waste everyone's time. If anyone in the audience disbelieves C, then articulation of such disbelief would show that the justification of X would not be valid absent further justification of C.

Note that it if the audience believes A, B, and D are true, then in the presence of such agreement, they would need no justification beyond assertion. Any doubts about B, however, whether particularly justified or not, would render the raw assertion insufficient to justify it. If one believes that B is true because of X, Y, and Z, and the audience would accept X and Z, but dispute Y, efforts to justify X and Z would again waste everyone's time. Asking the audience identify the particular points of disagreement will allow more efficient discourse shouldn't be seen as an effort to tip the scales in one's favor, but rather as an effort to use everyone's time as efficiently as possible.

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