Pierre-Joseph Proudhon was one of the most important and influential political theorists of the 19th century. On publication, Proudhon's first significant book What Is Property? created a sensation - in its pages, he declared 'I am an anarchist' and 'Property is theft!' The latter is Proudhon's - and potentially anarchism's - most famous quote, but maybe also the most misconstrued.

'When [Proudhon] says that property is theft, he's talking about the constitutional right to exclusive ownership ... In the world, everything belongs to everybody in common; you have to invent a principle to justify why I should have more than you. And as soon as you do that, Proudhon says, you deprive everybody else of ownership. The dispossessed become reliant on the owners for everything, to maintain their well-being and subsistence. And although they work and produce, they have to give up most of it to somebody else. That's the theft.' - Ruth Kinna

'The ultimate goal of Proudhonist doctrine, as a political project, coincides with that of Marxism, the thought of Saint-Simon, and anarchism: the end of the state ... A rehabilitation of Proudhon is necessary.' - Henri Lefebvre

'Proudhon remains an incomparable logician, one of the most vigorous thinkers of the age. All his books seem to be inspired by a deep love of humanity ... His disciples regard him as the master of the new politics, the prophet of modern society.' - The New York Times

'The first self-proclaimed anarchist and the founder of classic anarchist thinking.' - The Conversation

'In the English-speaking world, Proudhon is one of the best known but least well understood anarchists ... engage with his work and appreciate both the positive contribution he has made to anarchist thinking and the enormity of his influence on the anarchist movement.' - Ruth Kinna, author of Anarchism: A Beginner's Guide

'Proudhon was Europe's leading socialist thinker in his lifetime ... [Proudhon] defined anarchism both negatively (opposition to state and capitalism) and positively (vision of a bottom-up, federated, self-managed society and economy created by working class people themselves).' - Iain McKay

'Scholarship has largely ignored the insights of the first anarchist, Pierre-Joseph Proudhon. Proudhon's anarchism was a critique of the projects of national unification, universal dominion, republican statism and the providentialism at the heart of enlightenment social theory.' - Alex Prichard, author or Justice, Order and Anarchy: The International Political Theory of Pierre-Joseph Proudhon

'Proudhon is important because he's the first person to use the concept that everybody fears, anarchy, and define it positively. In doing so, he establishes the springboard for the anarchist movement. For him, anarchy is not, as conventional thought would have it, the corruption of democracy, it's something that we should embrace wholeheartedly. That's a huge statement to make.' - Ruth Kinna, professor of Political Theory, Loughborough University

'In 1870-71 Proudhon was acclaimed on all sides ... The ultimate goal of Proudhonist doctrine, as a political project, coincides with that of Marxism, the thought of Saint-Simon, and anarchism: the end of the state ... A rehabilitation of Proudhon is necessary.' - Henri Lefebvre