COMMENT | In late May and June, following the brutal death of George Floyd under the knee of a police officer in Minneapolis, mass protests against systemic racism took place across the US and around the world.

Floyd’s death followed many previous police killings of unarmed African-Americans who were not behaving violently. Most protests were peaceful, but some turned into riots with widespread looting and vandalism.

But while protesting against police brutality and racism is surely legitimate, can riots also be defended?

The most thoughtful philosophical defence of rioting is by Avia Pasternak of University College London. Pasternak defines a riot as “a public disorder in which a large group of actors, acting spontaneously and without formal organisation, engages in acts of lawlessness and open confrontation with law enforcement agencies.”

She adds that rioters typically cause damage to public and private property, as well as harming people, often in the course of clashes with police. Pasternak wrote before Floyd’s death, but her article provides a framework for assessing what took place after it.

Pasternak starts from the idea, familiar from discussions of ethics in war, that under certain conditions it is permissible to cause harm to others – even to innocent others – in order to defend oneself from an unjust attack. Commonly, three conditions are specified ...