Dictatorships and tyrannies may be casual about spilling their people’s blood, but not democracies. When the people get to decide whether to go to war, they rarely do so willingly. This was why Immanuel Kant said the spread of democracy was the best guarantee of world peace. As he wrote in 1795, “if the consent of the citizens is required in order to decide that war should be declared nothing is more natural than that they would be very cautious in commencing such a poor game”.

When contemporary thinkers such as Michael Doyle have tested Kant’s intuition, they have had to add a significant caveat: democracies may not like fighting each other – which is why war has become unthinkable between EU and Nato countries – but they can be very warlike indeed towards tyrants and ethnic cleansers.

Drones and cyberwarfare, the latest revolution in military technology, will force us to revise still further Kant’s connection between democracy, peace and war. Virtual technologies make it easier for democracies to wage war because they eliminate the risk of blood sacrifice that once forced democratic peoples to be prudent.