The theory of Marx and Engels was to promote a philosophical and scientific thought in the service of the communist movement. As a scientific theory it was totally discredited at the end of the last century with the collapse of the USSR. However, on the basis of the evident failures of the market economy, of the need for the constant use of war in international relations and of the patent destruction of the biosphere by capitalism, today we can confirm the truth of the prognoses of Capital on the long-term unviability of the capitalist mode of production. On the basis of this observation, this book proposes a recovery of Marxism as a critical theory of society, with the horizon of a new socialist society for the future of humanity.