Peter Kropotkin's _Mutual Aid: A Factor of Evolution_ represents one of the major contributions to twentieth-century political thought. A classic, though often misunderstood text of anarchist thinking, the book offers an exciting and viable alternative to our current political models. Kropotkin's idea of mutual aid is the radical practice of caring for each other while actively working to change the world. This new and authoritative edition of Kropotkin's important and unique contribution to the history of socialist ideas and anarchist ideology includes a critically informed afterword by Ruth Kinna that elucidates the book's relevance for today.