Appeal to Authority

What is an Appeal to Authority? 

One source claims; “Appeal to authority – (argumentum ad verecundiam) deductively fallacious; even legitimate authorities speaking on their areas of expertise may affirm a falsehood. However, if not using a deductive argument, a logical fallacy is only asserted when the source is not a legitimate expert on the topic at hand, or their conclusion(s) are in direct opposition to other expert consensus. Appeal to authority does not condone to agreeing to the argument.” **

**http://energyskeptic.com/2013/cognitive-bias/