Espousal is a formal noun for the act of taking up an idea and standing behind it, especially a political or moral one: the espousal of a cause, a policy, a belief. It names what you do when you espouse something — and that verb is the word people still use. The noun is rarer and a bit stiff, more at home in essays and newspapers than at the dinner table. Though actually, much older English used espousal for a betrothal or marriage, because it is built on the same root as spouse. Today, if you read “his espousal of …,” it almost always means public support, not a wedding.