Ulises Carrión (1941-1989) was a highly regarded Mexican conceptual artist whose work spanned performance, video art, and books. Carrión was a pioneering figure in the international mail art movement. His ability to build networks through mail art as well as through Other Books and So, the gathering space he founded and ran in Amsterdam, allowed Carrión to also champion his role as a cultural and social activist. His definitive essay, Mail Art and the Big Monster establishes the principles and goals of mail art, explains its evolution, and classifies it according to its formal characteristics and modes of circulation. Most important, it acknowledges the fact that, up to that moment, mail art depended on the postal system, and was thus able to “knock at the doors of the big monster.”