What I tell you three times is true
- Lewis Carroll

In DeMarco and Lister's classic book Peopleware, on page 53, they discuss unfounded claims that open-plan offices improve productivity:

The people who brought us open-plan seating simply weren't up to the task. But they talked a good game. They sidestepped the issue of whether productivity might go down by asserting very loudly that the new office arrangement would cause productivity to go up, and up a lot, by as much as three hundred percent. ... The only method we have ever seen used to confirm claims that the open plan improves productivity is proof by repeated assertion.
I have no idea if DeMarco and Lister originated the wonderful phrase "proof by repeated assertion", but they certainly helped popularise it in geek circles.

Proof by repeated assertion is repeating something over and over, without any actual proof, until everyone accepts it as fact. Repeated assertion of a proposition does not in itself make that proposition false, but it doesn't make it true either. If someone depends upon repeated assertion to the exclusion of real evidence, they may well be lacking any.

Here's an example: "Analogue vs Digital is not even an argument. One thing that is fact is that music that is recorded to analogue tape and then pressed to vinyl sounds better. No question. Digital is just not ready yet."

Proof by repeated assertion is an invaluable tool of propaganda. For political propaganda, you need mindshare in order for the debate to be framed on your terms. Getting people to believe the idea, for example, that invading and occupying another country (because they clearly have weapons of mass destruction) will reduce terror attacks, is the kind of big lie that can only be done by brazen repetition.

Insisting, say, that a particular group of detainees are bad people deserving of punishment, while repeatedly refusing to bring them to any kind of trial, is using repeated assertion of their wrongdoing as proof of it.

Repeated assertion is a key idea in advertising:

Most companies, when they run an advertising campaign, simply take the most unfortunate truth about their company, turn it upside down ("lie"), and drill that lie home. Let's call it "proof by repeated assertion." For example, plane travel is cramped and uncomfortable and airline employees are rude and unpleasant, indeed the whole commercial air system is designed as a means of torture. So almost all airline ads are going to be about how comfortable and pleasant it is to fly and how pampered you will be every step of the way.
- Joel Spolsky

Proof by repeated assertion is important in technology. Establishing your product as the "industry standard" and the competing vendor's offering as a "proprietary offering" when both are actually quite similar, requires repeated assertion.

See also

Another tried and true debating technique is brought to the gallows:

Proof by repeated assertion is repeating something over and over, without any actual proof, until everyone accepts it as fact.
Well, suppose for the sake of argument that we accept this self-serving "definition". Obviously this definition is loaded; an impartial definition such as
proof by by repeated assertion is a logical method of proof which proves a point many times by stating its veracity
would have been a better starting point for rational debate. But we can go along with the first "straw{berryFrog, man} definition" if we're careful to avoid propaganda. And we'll reach the expected conclusion: that PBRA is a perfectly good method for describing the truth, and one which cannot contradict itself.

Note that StrawberryFrog never states why PBRA is so bad, only that it is bad. E does this around 7 times, on top of an appeal to authority (that of the noted logician Charles Lutwidge Dodgson). Note in particular the deliberate association of PBRA with such "neutral" words as "propaganda", "big lie", "advertising" and "proprietary". But not a word on why PBRA is wrong. If PBRA were such a puddle of toxic sludge, we'd have seen arguments for that. But since PBRA is a perfectly good method for describing the truth, we're instead treated to propaganda poor enough to get its author kicked out of any advertising agency in the land, if only for the strange perception that one can argue against PBRA by using PBRA (as StrawberryFrog does).

Along the way, StrawberryFrog makes numerous other unsubstantiated claims. But that's OK -- after all, we've all heard zillions of times that open space, airline travel and vinyl are all bad, not to mention the "fact" that it is legitimate debating technique to accept a method only in order to invalidate it.

In other words, the only way StrawberryFrog manages to "debunk" (in e's followers' eyes, at least) PBRA is by resorting to PBRA hirself. Briefly put, the logical argument is this:

PBRA is bad. PBRA is bad. PBRA is bad. PBRA is bad. PBRA is bad. PBRA is bad. PBRA is bad.
Naturally, you can't use a logical technique against itself, as by doing so you'd deny yourself the capability to use it in the first place! So, while it may or may not be permissible to use PBRA to prove its own validity, it is definitely not permissible to use PBRA to deny itself. This truth is self-evident.

Evidently also to StrawberryFrog: e concludes by claiming that PBRA is akin to numerous invalid debating techniques, by prefixing them with a "noncommittal" "see also:". This part of the argument is another invalid variation on PBRA:

PBRA is like logical fallacy
And the proof of that?
PBRA is like proof by assertion
A syntactic tautology. OF COURSE a proof by repeated assertion will be like a proof by assertion, only better (depending on the number of repetitions)! But why is that wrong?
PBRA is like proof by handwaving
... and I can just imagine StrawberryFrog gesticulating to show this. Note that I'm typing these arguments for PBRA without moving my hands from the keyboard -- so much for "handwaving"
PBRA is like proof by intimidation
... and presumably I'll send goons after StrawberryFrog and e's followers?
PBRA is like domination techniques
but only to the extent that truth tends to be more convincing than made-up arguments.

Note that I don't even bother with explaining why PBRA is useful. Not just because that's obvious, but because StrawberryFrog has presented no case to answer against PBRA! Which leaves only one question. If PBRA is so bad, how come the only way to disprove it is to use it?

I let the reader judge.

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