Mutualism designates a group of anarchist philosophies that envision non-governmental society and non-capitalist commerce as the product of bilateral agreement and mutual guarantees between free individuals and social groupings. Historically, it predates anarchism as a term to describe the constructive counterpart to anarchists’ critique of authoritarian institutions. From 1840 until his death in 1865, Pierre-Joseph Proudhon produced a body of social scientific work contrasting the systematic exploitation inherent in existing governmental and commercial institutions with the possibility of a society based on mutual tolerance and ‘synallagmatic contract’. This analysis not only provided an explanation for how the exploitation occurs but also, he believed, demonstrated an already existing ‘mutuality’ of relations. As collectivist and communist forms of anarchist thought emerged, the term ‘mutualism’ became associated with non-communist forms of anarchism, including the individualism of Benjamin R. Tucker. The twentieth century saw the emergence in the United States of a more individualist form of mutualism, a ‘market anarchism’, and the present century has seen a continuation of the tradition that began with Tucker, in the ‘free market anti-capitalism’ of Kevin Carson. Meanwhile, more traditionally ‘Proudhonian’ mutualism continues to experience periods of renewed interest.