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Politics is ultimately about interests. Morals and highfalutin principles have their place, but a more reliable truth is that governments and countries usually act in their own self-interest. Usually. The way Israel greeted the visiting US vice-president, Joe Biden, this week offers an intriguing exception to the rule, a rare instance of a state acting in a way that brings itself almost no benefit and delivers a huge amount of self-inflicted harm.

Instead of embracing Mr Biden, Israel showed him the finger, choosing the very day of his visit to announce the construction of 1,600 new housing units in East Jerusalem. That counts as an in-your-face insult to a US administration that has demanded Israel freeze all settlement activity in the territories conquered in 1967, which...