What is the appeal to emotion fallacy?

Substituting feelings — stirring up fear, pity, anger, or excitement — for actual evidence, so people accept a claim because of how it makes them feel.

The pattern: favourable (or unfavourable) emotions are attached to X; therefore X is treated as true. It fails because how you feel about a claim has no bearing on whether it's true — if someone made you love the idea that 1+1=3, it still wouldn't be three.

A commercial shows beautiful, laughing people on a beach drinking a particular beer. The unstated argument is "you should buy this beer," and the "evidence" is the good feeling the imagery evokes.

This is the engine of most advertising and a lot of political rhetoric. Stirring emotion isn't always wrong — a coach firing up a team isn't making an argument — but the moment a feeling is offered in place of a reason, it's fallacious.

Tip: Specific named flavours include appeal to fear (scare tactics, ad baculum), appeal to pity (ad misericordiam), appeal to flattery, and appeal to spite — all swap an emotion for evidence.