Mter the impressive collapseoftheSovietUnionand the Eastern European socialist countries, it is more pertinent than ever to recover the scientific legacy ofKarl Marx. This legacy is mainly (if not exclusively) constituted by his work in the field of eco- nomic theory. Marx's economic theory was intended by his au- thor as a scientific objective theory about the nature ofcapitalist economies, a theory that was going to serve as the foundation ofthe critique ofbourgeois political economy. His "laws" about the demise ofcapitalism, like the tendency ofthe profit rate to fall or the lawofthe cyclical crises, have been shown to hold un- der certain conditions but not in general. At any rate, it is likely that had not the industrialized countries changed the situation ofthe working class, and allowed some intervention ofthe State in the economy (especially after the Great Depression), capital- ism would have hardly survived, even though it is impossible to guess what kind of regime would have been instaurated in its place. The present book is concerned with the very foundations of Marx's economics, hence with the very foundations ofhis scien- tific legacy. I hope that after reading the book the reader will be convinced that Marx's scientific work was indeed serious and that this is the time to recover it as an important paradigm in INTRODUCTION 2 scientific research. I think that the reader will be convinced that Marx's economic theory is no less serious and mathematically tractable than, say, general equilibrium theory.