It is time that our constitutional courts formally recognize what constitutional interpretation has created over two centuries. Of course constitutional law is limited by the document’s text. But we must interpret the text by finding principles that justify it in political morality, and we must test statutes against the text not by abstract semantics but by asking whether the statutes respect those principles. The Chief Justice’s reasoning contains an unwitting insight. The national power to tax is not just a mechanism for financing armies and courts. It is an indispensible means of creating one nation, indivisible, with fairness for all.

The Affordable Care Act’s mandate is not just another example of economic regulation of an interstate industry like cars or steel. It does not impose a tax in the ordinary political meaning. No one thought when the act was passed that Obama had broken his promise not to raise middle-class taxes: that claim is a sudden invention of opportunistic Republicans first denied and then embraced by Mitt Romney. But the act is nevertheless best understood as in the long tradition of mandatory insurance for the sake of justice.