Image via The Certified Shill

I spend a lot of time debating people on the internet, and, unsurprisingly, I frequently encounter people who make outlandish claims without providing any evidence to support those claims. In such situations, I typically ask them to present their sources, at which point they usually respond indignantly with something along the lines of, “just Google it,” “look it up yourself,” “do your own research,” or “so you expect me to do your work for you? I don’t think so.” However, as I will explain in this post, these responses are fundamentally flawed because they fallaciously shift the burden of proof and ignore the rules of logic.

The first major problem is simply that these responses misuse the burden of proof. The person making the claim always bears the burden and is responsible for providing supporting evidence, especially when their claim goes against the generally accepted wisdom. In other words, if I say, “aliens caused 9/11” then the burden is entirely on me to provide reliable sources to back up my assertion. You, in contrast, would be under absolutely no obligation to refute my claim or even take it seriously until I provided that evidence. So I could not tell you to “just Google it” because that would be placing the responsibility on you to debunk my claim, when in reality, the responsibility is on me to support my claim. To put it simply, you do not have to take a claim seriously until your opponent provides reputable sources to back it up. It is 100% their responsibility. So when people say things like, “so you expect me to do your work for you?” they have things totally backwards.

A useful way to think about this is to apply it to courtroom scenarios. The prosecution is the one making the claim or assertion (i.e., “person X is guilty”), so it is their responsibility to provide the evidence. The defense only has a responsibility after the evidence has been presented. In other words, the defendant does not need to prove their position (i.e., they don’t need to prove that they are innocent), rather they simply need to show that the prosecution’s evidence does not prove guilt. So the defense only bears a burden to defeat the prosecution’s evidence, rather than bearing a burden to provide evidence supporting their innocence. To be clear, there is certainly nothing to stop them from providing that evidence, but they aren’t required to do so. In other words, the prosecution must provide evidence of guilt, whereas the defense does not have to provide evidence of innocence.

The exact same rules apply in logical debates. Any time that you make a claim like, “X cause Y,” “Z is dangerous,” “studies have found X,” etc., you have just placed yourself into the role of the prosecution. At that point, it is your responsibility to provide evidence for your claim, whereas your opponent does not have to provide evidence refuting your claim. They are certainly welcome to do so, but they are under no obligation to prove you wrong until you provide evidence.

When you think about this in the context of a debate about science, the reason that the burden of proof works this way should become obvious. Imagine, for example, that I said, “studies have found X,” but I refused to actually provide you with such studies. How would you prove that I was wrong? Quite frankly, you couldn’t. You could show me that you failed to find such papers in any major database, but that wouldn’t prove that the studies don’t exist because they could simply have been published in a minor journal that isn’t well archived. See the problem? Proving a negative claim (e.g., “papers that found X do not exist”) is nearly impossible. It’s like trying to prove that Bigfoot doesn’t exist. It can’t be done because no matter how many trail cameras we put out, it is always technically possible that Bigfoot does exist and has simply managed to elude all of the cameras. That is why the burden is always on the person making the claim. I would be responsible for providing you with the papers that found X, just as Bigfoot hunters, UFO spotters, etc. are all responsible for providing evidence for their position. In other words, if one person says, “prove to me that Nessie, yetis, etc. exist” and the other says, “prove to me that they don’t,” the second person is being irrational because they are trying to shift the burden of proof. They are required to provide evidence for their position, not the other way around (note: you may notice that these arguments also contain an argument from ignorance fallacy, that is because shifting the burden of proof is simply a special case of that fallacy).

Via MythBusters Episode 187 “Bubble Pack Plunge”

Getting back to the original topic of simply telling people to Google something rather than actually providing them with the source, there is another serious problem there. Namely, Google is a mess. You can find websites supporting pretty much any quack position out there. So for any topic, you will be able to find “sources” supporting a given view, but those sources are often utter crap. As a result, simply telling your opponent to Google something is a terrible idea because they have no way of knowing specifically which sources you read. Imagine, for example, that you tell me that X causes Y and I should just Google it, so I do, but the first 20 or so results that I find are all from unreliable, quack websites. At that point, most people would probably stop looking, but the fact that the most popular hits are junk obviously doesn’t mean that there isn’t a good source out there somewhere. This is once again the problem of trying to prove a negative (i.e., trying to prove that a given source doesn’t exist). It is unreasonable to expect your opponent to spend hours looking for information to support your position. That is your job, not theirs.

Finally, knowing exactly which sources your opponent is basing their arguments on is extremely important, because if they are bad sources, then you can discredit their argument right there and then. To be clear, using bad sources doesn’t mean that the conclusion of the argument is wrong (that would be a fallacy fallacy), but it does mean that the argument itself must be abandoned until such time as reliable sources can be presented. Once again, the person making the claim must provide the evidence to support it, and until they do that, you are under no obligation to entertain their fanciful notions.

At this point, you might be thinking that is entirely unfair to expect people to have sources to back up all of their claims, and if you are thinking that, then that’s really too bad because this is simply how logical debates work. If you don’t have the sources to back up your claims, then you shouldn’t be debating people, because no one has to take you seriously until you provide your sources. It’s really that simple. Personally, I make lists and databases of sources on various topics, and every time that I read a useful new article, I archive it into my lists, that way I always have the sources ready to back up my positions. Microsoft Word or Excel are just fine if you want to make lists of URLs, but given that peer-reviewed publications are the relevant sources for most scientific debates, I recommend using a PDF organizer (I personally like Mendeley, which is free unless you need to store over 2GBs of PDFs).

The point in all of this is really quite simple: if you are claiming that something is true, then it is your responsibility to provide high quality sources to back up your position, and your opponent is under no obligation to refute your claims unless you provide those sources. Indeed, this entire post was summed up nicely by Christopher Hitchens in what has come to be known as Hitchens’ Razor, “What can be asserted without evidence can be dismissed without evidence” (or if you prefer the original Latin version, “Quod gratis asseritur, gratis negatur”).

Suggested further reading:
The Logic of Science — The Rules of Logic Part 5: Occam’s Razor and the Burden of Proof
RationalWiki — Burden of Proof
Science or Not — The reversed responsibility response – switching the burden of proof
Philosophy of Religion — The Burden of Proof
The Free Dictionary — Burden of Proof