When philosophers attack!
A Russian man was reportedly shot in a quarrel over the thinker Immanuel Kant. It sounds incongruous, but it's not the first time that philosophy has incited aggression.
Two men were waiting for a beer at a store in the southern Russian town of Rostov-on-Don. Somehow, the subject of the philosopher Immanuel Kant came up. Discussion morphed into argument, argument descended into fisticuffs.
What was it all about - a disagreement over synthetic a priori propositions?
Might the violence have been caused by diverse interpretations of transcendental idealism? Or perhaps the quarrel was triggered by a fundamental difference of opinion about the "categorical imperative"?
While the substance of the argument remains unclear, more details have begun to emerge.
One of the combatants pulled out a pistol, and shot the other one several times with rubber bullets before running away. He was later arrested and has been charged with causing serious bodily harm.
Kant, who wrote such works as the Critique of Pure Reason and Metaphysics of Morals, spent his entire life in the then capital of Prussia, Konigsberg (now Kaliningrad). That the technical (and often tortuous) prose of this 18th Century thinker could incite such ferocity might seem bizarre.
But philosophy and intense conflict are by no means strangers, as we can see from the behaviour of philosophers themselves.
A spat in 1766 between two other philosophical giants of the 18th Century, the Scotsman David Hume and the Genevan-born Jean-Jacques Rousseau, became the talk of intellectual Europe after Rousseau accused Hume of being behind an international conspiracy to blacken his name.
Hume had helped Rousseau flee persecution, but Rousseau detected base motives. "You brought me to England, apparently to procure a refuge for me, and in reality to dishonour me."
In 1946, the Viennese-born thinkers Karl Popper and Ludwig Wittgenstein met for their first and only time in a room in King's College, Cambridge (Bertrand Russell was also present). Popper was there to address a philosophy society on the topic of whether there could truly be any philosophical problems.
Crudely put, Wittgenstein held that all putative philosophical problems were merely puzzles caused by linguistic confusion. As Popper spoke, Wittgenstein became increasingly agitated.
At some stage he picked up a fireside poker and began to gesticulate with it. According to Popper - in a hotly disputed account - he demanded an example of a moral principle, to which Popper replied, "Thou should not threaten visiting lecturers with pokers."
Whereupon (again according to Popper) Wittgenstein threw down the poker and stormed out of the room, leaving Popper victorious on the academic field of battle.
That version of events was later challenged by an eye-witness and Wittgenstein disciple who accused Popper - in rather unacademic language - of being a liar.
Two of France's leading post-war intellectuals, Jean-Paul Sartre and Albert Camus, sometimes referred to as the "twin geniuses of existentialism", also had a spectacular falling out.
Once close friends, their rupture occurred in part over whether Marxism and existentialism were compatible, and about the justification or otherwise of violence as a means to political ends.
Despite, or perhaps because of, the nature of this latter dispute, their debate never became physical. But they showered each other in verbal vitriol in the pages of the highbrow magazine Les Temps Moderns during 1952 and their relationship never recovered.
To those who regard philosophy as just a load of old cant, conflict over abstruse theory might seem both perplexing and incongruous.
But to expect philosophers to behave better than anybody else hardly seems fair. Kant himself recognised, in one of his most famous lines, that humans were essentially flawed creatures: "From such crooked wood as that which man is made of, nothing straight is ever fashioned."
In any case, often at the core of philosophical squabbles are debates about matters of fundamental significance.
The Camus/Sartre antagonism played into the agonised national conversation about the extraordinary violence of the Algerian war.
There were atrocities on both sides - the French army engaged in routine torture of Algerian fighters for independence. The Algerian-born Camus had ambivalent views, while Sartre became a leading opponent of French policy.
Kant's writings are highly relevant here, too. It's hard to imagine that today's modern conception of human rights would exist without the Prussian genius.
Kant's deontological approach to ethics - the idea that there are some things that are impermissible whatever the consequences - rules out torture. There is "a categorical imperative" against torture in all circumstances.
An alternative approach to ethics, utilitarianism, contemplates the possibility that torture might be acceptable where, for example, it could save many lives.
Perhaps this is what lay behind the brawl in Rostov-on-Don? It seems rather unlikely that the firing of bullets - rubber or otherwise - could survive any interpretation of Kant's categorical imperative.
So we can only deduce that the shooter was not a Kantian.
David Edmonds is the co-author of Wittgenstein's Poker and Rousseau's Dog and co-runs the website Philosophy Bites.