Logical Fallacy – Shifting the Burden of Proof

While casually reading a thread in a comments section of the James Webb Space Telescope page, I saw a clear example of a logical fallacy which will make for an easy and short post. The point of stating the obvious here, as some will see it, is that these flaws in arguments are not always obvious to people. Furthermore, they can be much more subtle and found within topics that matter to public health too. These mistakes in reasoning in fact permeate every and any topic, and they are inherently the kinds of problems which stunt ‘debates’ or productive, truthful discourse.

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Dark Matter: Context

The example I’m using is brief and clear, but this first part gives context to the exchange.

Commenter A:

The part to take issue with is:

“Just like Dark Matter being proven to not exist, yet many still think it exists.”

They seem to have decided they know this for certain. One assumption they make is that dark matter was ever an established and defined substance. It never was, and still isn’t. Dark matter is a placeholder term accounting for something we don’t yet know (be that an all new phenomenon or a modification to the standard laws of general relativity). As a placeholder, it could most plausibly explain the effects we have observed, which would be consistent with all current observations.

Do many ‘still think it exists’? Well not as resolutely as he puts it. That is, physicists haven’t identified ‘it’ but rather point out that ‘all the data suggests an unknown phenomenon which would in theory account for what all our observations seem to infer’.

Not a snappy line, but that’s why you can’t sum it up as simply as the commenter does. In short, when the scientific community accepts the likely existence of dark matter, they are not claiming to have defined it; just that there is something there which must be affecting the stuff we can see, which we haven’t been able to account for (after all other known phenomena is accounted for).

Right, now that bit is done, onto the specific fallacy.

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The Logical Fallacy(s)

Commenter B:

A perfectly reasonable response, given that the comment went against the scientific consensus and threw up several unwarranted assumptions, with nothing to back it up.

The thing is, the first commenter claimed that we have proof that dark matter doesn’t exist. You can’t prove a negative though, this is basic logic. An analogy would be that while no one has ‘evidence’ or ‘proof’ that magical unicorns exist, we can all safely proceed as though they don’t, because there’s no reason to assume it.

However, with dark matter, there is fair reason to infer it. Again, ‘dark matter’ being an ‘unkown’. While no observations infer the existence of unicorns, there are scientifically consistent observations to infer the existence of an unknown influence on the cosmos.

Therefore, the second comment is a fair question, as most of the literature actually suggests the opposite of what he is claiming.

Commenter A’s response:

Here is where the switch happens. He now in fact commits two fallacies in one.

Fallacy 1 – The Burden of Proof

Definition:

He made the claim that there’s settled science disproving dark matter, but now says it’s the second persons responsibility to disprove him. This is switching the burden of proof and arguing in bad faith. They are not discussing proving that a definition of dark matter exists, they are discussing his claim that there is proof that it (whatever he assumes it is) doesn’t.

To borrow Carl Sagan for a moment, if I claim there is an invisible dragon in my garage, it is up to me to prove that – not the person I’m telling.

Fallacy 2 – The Complex Question Fallacy

Definition:

While not phrased as a question, this was the closest one I could find. They are assuming within the statement that someone argued they’d ‘proven’ the existence of dark matter, but no one made this claim.

It’s arguably a false dichotomy in that he would therefore imply that because the second commenter can’t provide a paper proving its existence, then that must mean he doesn’t need proof to conclude that it definitely doesn’t exist. But as Carl Sagan also put it:

“Absence of Evidence does not mean Evidence of Absence”

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Conclusion

Despite me choosing to give some context around dark matter, you don’t need to know the first section in this post to spot the fallacy - although it helps if you already detected these errors in the first comment.

In fact, logical fallacies used in this way simply shut down conversations and offer no substance or credibility. That’s why there is no point posturing with knowledge of the topic; you have to communicate with intellectual honesty before getting into that. This is precisely why it’s as important to recognise the wrong things people say, as it is to recognise the right.

It’s no use arguing if you can’t agree on what is logically correct, on how to reason. Ignoring these rules can (and frequently does) break down further into not ‘agreeing’ on what a fact is, what constitutes strong or weak evidence, and what is not factual.

To that end, opinions, lies, and beliefs can appear ‘factual’. Trust in expertise is eroded in the public eye, and real data can be hand-waved aside to be replaced with what feels good. Truth matters. Truth is dependent on logic and reality. Correct reasoning and logic should lay the foundations of honest discussion.