Achille Nicolas Isnard (1749-1803) an engineer with a keen interest in political economy, is best known for demonstrating the concept of market equilibrium using a system of simultaneous equations. The breadth and depth of his work undoubtedly established him as one of the forerunners of modern mathematical economics, yet his seminal contributions to the study of economics remained largely unrecognized until the latter half of the twentieth century. This pioneering new book, the first in English, examines Isnard's life and illuminates his major contributions to political economy. It contains substantial extracts from a number of his publications presented both in English translation and in the original French so Isnard can now finally achieve his place at the heart of discussion on the origins of mathematical economics. The diverse issues covered here will ensure that this book appeals not only to economists with an interest in the history of mathematical economics, but to anyone interested in the emergence of political economy and in wider social thought during the Enlightenment.