Moving the goalposts is a form of inefficient argument/discussion which may at times be considered a form of trolling. It consists of raising an objection, insisting that the objection be met, and then changing the objection to dodge any attempted refutation.

"Okay, if you want to defend evolution, show me an example of something that's evolved"

"Well, corn used to look a lot more like grass; we've selectively breed it to the point where not only is it a completely different plant, but a plant that could not reproduce without our help. That shows that it couldn't have existed in the Americas in its current form before humans appeared -- it must have evolved to its current form within the last 50,000 years."

"Human guided breeding doesn't count. Give me an example of natural evolution."

"Well, we have fossils of hominids going back millions of years, moving from early apes to humans."

"But there are lots of apes, and lots of them look kind of like humans. Why would you think that something that looks more like a chimp than a human evolved into a human?"

"Because we have examples of apes changing through time to become more and more like humans -- and others changing to become more and more like modern chimps -- which appear ordered in time and space to indicate progressive change."

"But there are lots of gaps in the fossil record. Why would you trust it?"

In some ways, this is a perfectly okay conversation; the questioner started out asking for examples of evolution, and finished up asking for a detailed analysis of physical anthropology -- a thought process entirely consistent with a curious person of high intelligence.

On the other hand, the conversation seems to be focused on objecting and protecting a weak position, and not with learning a new and interesting viewpoints. Because this judgement is somewhat subjective -- one person's confused question is another person's obnoxious contrarianism -- it is possible for either party to mistake what is going on. Unfortunately, we have completely failed to develop a social norm encouraging people to ask things like "what do you think, is this conversation helpful to you in developing an understanding of evolution?".

Moving the goalposts is often said to be an informal fallacy, although I'm not certain that that is accurate. It is, however, an improper and counterproductive way to learn more about the universe, and should be discouraged.

Moving the goalposts may be entangled with the No True Scotsman fallacy or slothful induction, among others. It is also a common tool used in sealioning.

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