Book excerpt: John Finnis's proposal to rehabilitate Aquinas's natural law theory as an appropriate foundation of legal and moral theory rests on the assumption that Aquinas's theory can be restored by eliminating the mistaken interpretations of subsequent natural law theorists. This book challenges that assumption. After a brief analysis of Aquinas, the theories of Suárez, Grotius, and Pufendorf are investigated. It is argued that their theories are no 'mistakes', but attempts at solving problems inherent in natural law theory. As these attempts all fail, tensions remain, and ultimately lead to the demise of the theory. Finally it is argued that Finnis, running into the same problems, cannot hope to restore Aquinas's theoretical edifice.