Pierre Jacob is one our (rare) alalytical philosophers. His book, published simultaneously in English by the Cambridge University Press and in French, seeks to resolve two fundamental questions :The first is a dilemma : if on one hand, things have meaning and if on the other, our representations are cerebral processes endowed with physical, chemical and biological properties, how can we conciliate the two ? Pierre Jacob shows how we can resolve this dilemma by providing giving semantic properties to cerebral processes.The second question stems from the body/mind problem : can our representations explain our behaviours ? Pierre Jacob shows how the solution to the preceeding dilemma makes it possible to give this question an affirmative response.At the same time, he also makes a very original contribution to the book by offering a magistral exposé of the current thought process concerning these questions in the domain of analytical philosophy.Pierre Jacob, philosopher, is director of research at the CNRS.