The Burden of Proof

Why is it that few people seem to have problems with the burden of proof when it comes to the innocence or guilt of a murder suspect, but then cannot apply the same exact logic to more esoteric issues, such as the existence of ghosts, gods, and the like?—Massimo Pigliucci, 2010

Most people as young children appear to have a “commonsense” understanding of the burden of proof. When young people hear a claim being made and it is, in their minds and experience, an extraordinary claim being made, quite often the response is one of asking for something to support the claim. The most common retorts are along the line of “Prove it”, “What makes you say that”, “Show me” or something like “Oh, yeah?”. Somewhere along the way too many humans lose that sense and too often suspend their inclination to accept the principles underlying the “Burden of Proof”.

Going a bit further it is to be noted that not all people care to be considered as being rational or reasonable or willing to use their intellect as best as possible but for any person who cares at all about being rational and using reason then operating with the “Burden of Proof” rule of reason:

You cannot claim that “miracles exist unless someone proves that they do not exist.” 

You cannot claim that “souls exist unless someone proves that they do not exist.” 

You cannot claim that “angels exist unless someone proves that they do not exist.” 

You cannot claim that “deities exist unless someone proves that they do not exist.” 

The Burden of Proof as presented below applies to claims that are cognitive and empirical.  The principle applies to claims about what exists or does not exist.  

The instances of circumstances that provide nuanced exceptions (see below) to the rule are so few and misleading to let it appear they nullify the rule that it is far better to just state that the burden of proof is always on the claim that X exists rather than on the claim that X does not exist. It is a fallacy to claim that X exists unless you prove that there is no X.  What is improper is for a person to claim that “X exists” and when asked to prove it, then the person who made the claim uses as a defense of “X exists” the next claim that no one has proven that X does not exist.

If a person claims that X exists and is real then the burden is on that person to supply some support for that claim, some evidence or proof that others can and should examine before accepting it. It is incorrect to think that X exists and is real until someone can prove that there is no X. It is also wrong to think that just because you can not prove that X exists that does not mean that X does not exist and therefore X does exist.

Why is it that the burden is on the person who makes the claim?  Well think whether or not it is a better way to proceed through life to accept anything and everything that people claim to be so.  Experience should instruct every thinking human that there is a high probability that not everything that people claim to be true is actually true.  Some claims might be made with the claimant aware that the claim is not true and some claims might be made with the claimant thinking that they are true but being mistaken.  As it is for most humans not a very good idea to proceed through life based on beliefs that are false and thinking beliefs and claims to be true when they are not, most humans and those who would use reason to guide them will want some evidence and reasoning to support a claim being asserted to be true.  So the burden is on those who make claims to offer reason and evidence in support of those claims.


The burden of proof is always on the person making an assertion or proposition.  Shifting the burden of proof, a special case of argumentum ad ignorantium, is the fallacy of putting the burden of proof on the person who denies or questions the assertion being made.  The source of the fallacy is the assumption that something is true unless proven otherwise. 

The person making a negative claim cannot logically prove nonexistence. And here’s why: to know that a X does not exist would require a perfect knowledge of all things (omniscience). To attain this knowledge would require simultaneous access to all parts of the world and beyond (omnipresence). Therefore, to be certain of  the claim that X does not exist one would have to possess abilities that are non-existent. Obviously, mankind’s limited nature precludes these special abilities. The claim that X does not exist is therefore unjustifiable. As logician Mortimer Adler has pointed out, the attempt to prove a universal negative is a self- defeating proposition.  These claims are “worldwide existential negatives.” They are only a small class of all possible negatives. They cannot be established by direct observation because no single human observer can cover the whole earth at one time in order to declare by personal authority that any “X” doesn’t exist. 

see also: The reversed responsibility response – switching the burden of proof, Science or Not December 4, 2012

Burden of Proof

From  X, which is the assertion, is not yet disproved. Therefore, X. 

This is a Fallacy.  If X is unproven, then it is unproven and remains unproven until reason and evidence is provided or secured to establish the proof or high probability of the claim being true.. 


(1)Of course God exists. Has anyone ever proven otherwise?

(2)Of course pink elephants inhabit Mars. We don’t see them because they blend in. Can you prove otherwise?

(3) Of course Santa Claus exists. No one has ever proved, to my knowledge, that Santa Claus does not exist. And if one were to fly to the North Pole and say: Well, look, there’s no toy factory there. A believer could argue: Well, Santa Claus knew you were coming and moved his operations to the South Pole. So you fly down to the South Pole. No Santa Claus factory, toy factory there. So the believer would say: Oh, he moved it back up to the North Pole.

(4) Of course  leprechauns exist. Has anyone ever proven otherwise?

(5) Of course  ghosts exist. Has anyone ever proven otherwise?

(6) Of course yellow polka dotted aliens exist. Has anyone ever proven otherwise?

(7) Of course  X  exist. Has anyone ever proven otherwise? 

Proof of a Negative Claim

So you simply cannot prove general claims that are negative claims — one cannot prove that ghosts do not exist; one cannot prove that leprechauns too do not exist. One simply cannot prove a negative and general claim. 

“Negative statements often make claims that are hard to prove because they make predictions about things we are in practice unable to observe in a finite time. For instance, “there are no big green Martians” means “there are no big green Martians in this or any universe,” and unlike your bathtub, it is not possible to look in every corner of every universe, thus we cannot completely test this proposition–we can just look around within the limits of our ability and our desire to expend time and resources on looking, and prove that, where we have looked so far, and within the limits of our knowing anything at all, there are no big green Martians. In such a case we have proved a negative, just not the negative of the sweeping proposition in question.”-Richard Carrier, “Proving a Negative “(1999) by Richard Carrier  at

It is possible to prove rather specific negative claims that are made with rather well defined limits.  If the area to be searched is well defined and of a reasonable size that permits searching then a negative claim might be capable of being proven.  For example, if one claims that there is no apple in the top desk drawer of a desk then all one needs to do is to open the top desk drawer indicated in the claim and examine it for its contents.  Finding no apple therein would provide sufficient evidence under ordinary circumstances to verify or confirm the negative claim that there is no apple in the top desk drawer. In this regard Irving Marmer Copi writes:

“In some circumstances it can be safely assumed that if a certain event had occurred, evidence of it could be discovered by qualified investigators. In such circumstances it is perfectly reasonable to take the absence of proof of its occurrence as positive proof of its non-occurrence.” – Introduction to Logic, Copi, 1953, Page 95

You can prove a specific negative claim by providing contradictory evidence. An example of a proof of a rather specific negative claim by contradictory evidence would be if someone were to claim that the one and only watch that you own is in the top drawer of the desk.  You make the negative claim that it is not in the drawer and you see it clearly on your wrist.  There is no need to look in the drawer.   

You can also prove specific negative claims when they involve known impossibilities.  For example is someone were to claim that the one and only moon that normally orbits the planet earth was in the top desk drawer.  You claim that the moon is not in the desk drawer.  There would be no need to look inside because the mass of the moon would not fit inside such a space and were its mass to be condensed its mass would be far greater than the desk could support were the desk made of ordinary earth substances. 

You can also prove specific negative claims that can be rephrased as a positive claim.  If someone claims that the lights are not on in room 442 that claim can be rephrased as claiming that the lights are off in room 442.

The claim that you can not prove a negative claim is itself a negative claim and would be a self defeating statement or a retortion were it not generally understood to be a limited claim.  What is usually meant by the assertion that “One can not prove a negative claim” is that it is not logical to insist on proof of claims or statements of the sort: ” There is no such thing as X that exists anywhere at all and at any time at all.”

Negative claims in the context of religion are very commonly of this form:

  • “You can not prove that there is no deity”
  • “You can not prove that there are no miracles”

These claims are asserted by those holding belief in the existence of such phenomena.  They do not usually assert such criticisms against those who claim that there are no phenomena such as those not believed in by the defenders of the existence of a deity or miracles.  For example believers in deity or miracles do not criticize those who claim that there are no tooth fairies or that there are no leprechauns.  The theists appears to think that the critic of theism is claiming that there are no deities and that such a claim can be proven or has been proven.  What is actually being claimed by most critics of the claims that there are deities or miracles is that “There is not sufficient evidence to establish the existence of a deity or a miracle.”  or that “It has not been proven that there are deities or miracles.”  The burden of proof is on the claimant of the positive claim that an entity X does exist.  The critic of the person making the positive claim that an entity X does exist is asking for evidence in support of that claim and that the evidence be relevant and sufficient to warrant or support the claim.

The unprovability of non-existence.Here’s what the The Objectivist Newsletter (April 1963) had to say on the logical fallacy of proving a negative:”Proving the non-existence of that for which no evidence of any kind exists. Proof, logic, reason, thinking, knowledge pertain to and deal only with that which exists. They cannot be applied to that which does not exist. Nothing can be relevant or applicable to the non-existent. The non-existent is nothing. A positive statement, based on facts that have been erroneously interpreted, can be refuted – by means of exposing  the errors in the interpretation of the facts. Such refutation is the disproving of a positive, not the proving of a negative…. Rational demonstration is necessary to support even the claim that a thing is possible. It is a breach of logic to assert that that which has not been proven to be impossible is, therefore, possible. An absence does not constitute proof of anything. Nothing can be derived from nothing.” If I say, “Anything is possible” I must admit the possibility that the statement I just made is false. (See Self Exclusion) Doubt must always be specific, and can only exist in contrast to things that cannot properly be doubted. “