The reason a metaphor smuggles a premise

Call a budget a diet and the argument for cutting is already made: diets are voluntary, virtuous and temporary, and the fat is distinguishable from the muscle. None of that was demonstrated about the budget. It came in attached to the word.

What everyone sees

Metaphor is filed under style, a way of making an abstract point vivid, with the real argument sitting elsewhere in the literal sentences. The comparison is not a wrapper. It imports a set of relations from the source domain, and those relations then do inferential work that nobody has to defend because nobody stated them.

What is actually happening

Lakoff and Johnson argued that conventional metaphors structure reasoning rather than ornament it — treating argument as war licenses attack, defence and territory, and makes cooperative framings feel like evasions — and that the imported structure is invisible precisely because it is conventional. Ottati, Rhoads and Graesser found that metaphor also changes how a message is processed rather than only what it says, with a familiar metaphorical frame increasing engagement with the argument for audiences already interested in the topic. The combination is what makes the device efficient. The comparison supplies premises and simultaneously raises the audience’s appetite for the argument those premises support.

Why it stays hidden

The smuggling hides because objecting to a metaphor sounds pedantic. The person who says the budget is not a body is heard as missing the point, which protects the premise better than an argument would. The imported structure then survives into policy language, where it is no longer recognisable as a comparison at all.