Sophistry
No. 15 Rhetorical trick

Moving the Goalposts

Raise the bar for proof each time the current bar gets met.

A measuring scale with a bar reaching one post, and a second post set further along it. c a b
FIG. 15a, the evidence produced. b, the standard it was asked to meet. c, the standard demanded once b was met.

Illustrative example

"Show me one peer-reviewed study." (shown one) "Well, one study isn't enough, show me a meta-analysis from the last year."

Moving the goalposts sets one standard of evidence, then quietly raises it the moment that standard is satisfied, so the conclusion can never actually be reached.

This isn’t the same as reasonably asking follow-up questions. The tell is that the new standard wasn’t mentioned until after the old one was already met.

Ask the person to state, up front, exactly what evidence would change their mind. If that keeps shifting after each answer, the goalposts are moving.

Seen in the wild

Real, sourced instances of this technique in actual public debate.

Examples are chosen for how clearly they show the technique, not for who said it.

Donald Trump

Leans right

Businessman and prospective presidential candidate

Read together
The demand was met

“An 'extremely credible source' has called my office and told me that @BarackObama's birth certificate is a fraud.”

August 6, 2012 (Twitter)The original post, catalogued with the rest of the timeline by FactCheck.org (opens on the source site)

WatchTrump in New Hampshire the day the certificate was released (opens on the site hosting the footage)
And again, two years on

“I was the one who got Obama to release his birth certificate, or whatever that was!”

June 2014 (Twitter)FactCheck.org timeline of the claims made after the release (opens on the source site)

Context
Trump spent the spring of 2011 publicly demanding that President Obama produce his long-form birth certificate. Obama released it on April 27, 2011. This came fifteen months after the document Trump had asked for was published.
Reading
A specific, checkable piece of evidence was demanded. It was produced. The response was not to accept it or to give a reason for rejecting it, but to declare it forged and carry on. Once the standard of proof can be revised after the proof arrives, no evidence can ever settle the question, which is the point.

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