One-way hash argument

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A one-way hash argument is a fallacious style of debate where one party makes a simple (or simple-sounding), yet typically dishonest assertion that is difficult and time-consuming for their opponent to rebut. The phrase was first coined by Julian Sanchez of the Cato Institute, who had noticed similarities between the debating style of global warming denialists and creationists.[1]

It derives its name from a kind of mathematical function used to generate fairly-unforgeable cryptographic signatures. In an extremely ironic example of what happens when you let laypeople anywhere near complicated technical terms, Sanchez used "one-way hash" to refer to something that was not actually a one-way hash,[note 1] which in turn was the wrong analogue for the type of argument he was trying to describe.[note 2] This error goes right over most laypeople's heads, thus neatly illustrating Sanchez's own point:

The talking point on one side is just complex enough that it's both intelligible — even somewhat intuitive — to the layman and sounds as though it might qualify as some kind of insight. …The rebuttal, by contrast, may require explaining a whole series of preliminary concepts before it's really possible to explain why the talking point is wrong. So the setup is "snappy, intuitively appealing argument without obvious problems" vs. "rebuttal I probably don’t have time to read, let alone analyze closely."

Sanchez states that the aim of a one-way hash argument is to persuade the general public, which is not particularly well-versed about the topic under discussion:

I can often make a convincing case for absolute horseshit. A specialist would surely see through it, but in an argument between us, the lay observer wouldn’t necessarily be able to tell which of us really had the better case on the basis of the arguments alone — at least not without putting in the time to become something of a specialist himself.

So basically, the goal is toss out bullshit that sounds halfway plausible to those without the education to know better.[note 3] Creationists absolutely love one-way hash arguments. So too do Moon landing denialists.

Another related concept is the "soundbite". A common complaint within contemporary politics is that politicians are increasingly having to speak in simple, snappy "soundbites", with less and less of a place in the public sphere for longer, more reasoned arguments.

See also[edit]


  1. He was actually describing a specific kind of one-way function used for actual encryption, rather than the one-way or cryptographic hash functions used in cryptographic signing. While the one-way function is reversible, the cryptographic hash function is not.
  2. The particular one-way function referred to (multiplication of large prime numbers) is not the correct analogue to the "one-way hash argument" in that it is possible to compute its inverse quickly if you have a "key," which is not really true of a "one-way hash argument;" an accurate analogy would be with other classes of problems for which no such keys exist. Unfortunately, only a few mathematicians and other theorists care about the problem classes in question — forget having to explain "preliminary concepts," there are people with doctorates in this field who do not have a proper grasp on this.
  3. Incidentally, the Republican Party is going to great lengths to ruin the public education system. This is probably not a coincidence; they're all charlatans who want to ensure that the bulk of the population are highly-credulous suckers.


  1. Julian Sanchez. "Climate Change and Argumentative Fallacies." April 6, 2009.