Moving the Goalposts

Logical fallacy

Raising the standard of proof once the original standard has been met, so that no amount of evidence is ever sufficient.

An everyday example

“Show me one study. Now show me a replication. Now show me one in humans.”

The same move in this debate

“Show me a healthy vegan. Now show me a vegan athlete. Now show me one who has done it for forty years.”

Where this appears

You can survive on it, but you won't thriveHealth & Nutrition

Arrives once the question of whether a vegan diet is adequate has been settled, replacing it with a standard nobody was defending and which almost nobody on either side actually meets.