Moving the goalposts

Moving the Goalposts is a debate fallacy in which you continually re-define the point of the discussion to avoid your opponent being able to provide a correct answer. Most often seen in Evolution vs Creationism debates. "Show me a transitional fossil between a whale and a fish." example shown. "Show me transitionals between those transitionals and each others." examples shown. "Show me the transitionals between THOSE samples and each other."

Repeat ad absurdium.

This tactic is a sure admission that the person using it knows their position is untenetable, but refuses to admit defeat.