Bangladesh, Feb. 13 -- Every February, on Abraham Lincolns birthday, Americans rehearse a familiar liturgy. Lincoln is praised as the Great Emancipator, the savior of the Union, the embodiment of moral clarity and constitutional restraint. He stands as the reassuring proof that democracy can survive its gravest crises without stepping outside its own principles.

There is truth in this image—but it is an incomplete truth, and in our own moment, a potentially dangerous one. For Lincolns greatness did not consist in a simple fidelity to law. It consisted in something far more unsettling: his recognition that when a social order has already collapsed under the weight of its contradictions, legality itself can become an obstacle to just...