(This post has been rewritten and reposted with corrections since its original publishing date)
Hey, guys. This post deals with that favorite specious rhetorical tactic of science-deniers and middle-school debating clubs everywhere, the Moving Goalpost.
This fallacy is functionally similar to an American football game in which the player carrying the ball is faced with goalposts that are continuously receding, and no matter how fast he runs or how far he throws the ball, they are always out of reach.
This tactic is one in which ever further-out-of-reach standards of proof or evidence of a claim are used, and the more difficult to meet, the better. Should the requirement for evidence somehow be met, these criteria are then arbitrarily revised to be even more stringent and unreasonable than before, rather than acknowledging that the originally stated criteria have been met.
This fallacy involves redefining one’s claims to put them conveniently out of reach of any possible falsification.
It’s simply a time consuming and extremely roundabout way of answering the question, “What evidence would change your mind about X?” with the statement, “No evidence you can possibly present would ever be enough to convince me!”
This tactic is a favorite of creationists, electric universe proponents, anti-vaccinationists, HIV-deniers, global climate-change contrarians, and Alt-Med advocates, and any other ideologically-motivated denial of uncomfortable or inconvenient facts.
Below are a couple of examples of this in use:
- Show me just one experiment conducted in a lab on Earth that has ever produced dark matter, directly measured the effect of gravity, created a black hole, a working example of stellar fusion, or replicated the effects of dark energy at laboratory scales!
The above is an excellent example of moving the goalposts out of reach from the very beginning, and there’s the following, in which the requirements for evidence recede each time the argument reused:
- I want to see just one example of a transitional species between fish and tetrapods before I can accept evolution!
- Tiktaalik? Now you have two more gaps in the fossil record to fill between Tiktaalik and whatever existed before and after it!
- What? You’ve filled in those two gaps? Now you have four more gaps to fill! You still haven’t met my requirements! This proves evolution is a sham!
In any constructive discussion, it’s important to state up front just what evidence you will accept for a claim of fact, and to stick with it throughout the discussion rather than making it closer to the point of impossibility to achieve and finally, admit when the standards of evidence have been met.
It should be apparent from these examples that many fringe-proponents can never admit that they are wrong, when demanding ‘just one proof’ and then demanding ‘just one more proof’ and so on, since for champions of Revealed Truth™, it simply wouldn’t do to do something as unbecoming as changing one’s mind.
Cranks, deniers, and fringe theorists often like to claim that they are open to evidence, and that they could be mistaken, but when it comes right down to it they show themselves to be as closed-minded as they like to project onto their critics.