This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book discusses the different and conflicting ways in which late neoclassical approaches produced the concept of market failures and mobilized it to understand the economic institutions in general and firms in particular. It establishes that the transitions from the study of perfect competition to that of imperfect competition and from market exchange to economic institutions do not add up to a radical break from the neoclassical problematic. The book focuses on the treatment of the concept of the human subject in late neoclassical economics and offers a critical evaluation of the accentuated pre-occupation of late neoclassical economists with the motivational and cognitive dimensions of the assumption of rationality. It presents the trajectory of a transition from the concept of Nash equilibrium associated with classical game theory to the concept of evolutionary stability associated with evolutionary game theory.