MOSCOW (AP) — An argument in southern Russia over philosopher Immanuel Kant, the author of “Critique of Pure Reason,” devolved into pure mayhem when one debater shot the other.

The state news agency RIA Novosti on Monday cited police in the city of Rostov-on-Don as saying the argument took place in a small store and deteriorated into a fistfight. One participant pulled out a small nonlethal pistol and fired repeatedly....