This book provides analytical arguments that demonstrate the necessity to go beyond not only mainstream economics but also, and especially, the capitalist economy itself. It provides a radical critique of mainstream economics, comparing it to an unscientific form of single thought, and applies this criticism to the specific fields of growth, development, the institutions, defense, or the environment. It targets both neoclassical economics and reformist "soft heterodox" currents, from neoinstitutionalists to neo-Keynesians-including Thomas Piketty or Amartya Sen, among others. In doing so, it rejects Keynes' theories of money, the crisis, and the state. It then offers a Marxist interpretation of the current crisis of capitalism, considering it as a systemic crisis without solutions internal to its own logic and dynamics, and emphasizes the links between this capitalist crisis and imperialist wars, and the destruction of the environment and natural resources by capital. The book concludes by arguing that we must find the necessary theoretical and practical alternatives in a Marxist perspective, advocating for socialist transitions away from the capitalist economy to protect humanity and the environment.