People go on about the three necessities of life being food, shelter, and love. But there's one that's so essential that people don't even begin to mention it: oxygen.

After all, you can't eat, house yourself, or snuggle when you've asphyxiated. (Grim, but true.)

Madison, in one of the snappier moments of Fed 10, uses an analogy to try and calm people down about all the Anti-Fed gossip that they were out to make themselves kings—he had to, at the very least, assure people that they thought liberty was absolutely necessary, even if they weren't too keen on all of its side-effects.

To do so, he drops this gem:

Liberty is to faction what air is to fire, an aliment without which it instantly expires. But it could not be less folly to abolish liberty, which is essential to political life, because it nourishes faction, than it would be to wish the annihilation of air, which is essential to animal life, because it imparts to fire its destructive agency. (10.5)

This is a pretty simple analogy. Liberty, like the air we breathe, is essential to political life. However, liberty gives us the power to form factions and try to bash the other factions against the wall.

But, you can't get rid of air to put a fire out, and likewise you can't get liberty.

The analogy's not only easy to understand, but it also follows a lot of Revolutionary Era rhetoric about liberty being as essential to people as breathing, in the face of political oppression. Madison, with this analogy, is basically trying to calm people anxious about the new federal government by saying, "Hey, we think liberty is essential too, and we're not trying to get rid of it. Cool your jets."