Economic thought has suffered, over the past centuries, remarkable progress and, despite the fact that the contemporary world is characterized by the existence of distressing problems in many regions of the planet, such as diseases, misery, hunger, unemployment, incomprehension among peoples leading to wars and the latent state of international tension and violence, understood in its broadest sense, undoubtedly all currents of economic thought, throughout history, from Greek and Roman philosophers, to the scholastics of the Middle Ages, to mercantilists (these not much clearly), by 18th century liberals, by 19th century socialists and more recently, in the 20th century, by John Maynard Keynes (1888-1946) and Milton Friedman (1912-2006), emphasize the need to seek a more just, free and balanced world where man can have access to growing social well-being, materialized in the continuous meeting of his socio-political-economic needs and in the development of his spirit.The reasons for not fully achieving these goals - despite the remarkable scientific and technological progress achieved by Humanity - may lie in the nature of the human being himself, unequally endowed with aptitudes, desires and goals, an insatiable conqueror and increasingly self-centered.However, this moral and philosophical stance of great thinkers gives encouragement to those who envision a better world and, although the recipes are different - throughout history there has been a huge diversity of ideas and systems, many of them totally antagonistic (some liberal, others centralizing) - the ultimate goal is always the good of humanity.In this book, we present some ideas that we consider fundamental to understand the thinking of four great Men - Adam Smith (1723-1790), Karl Marx (1818-1883), John Maynard Keynes (1883-1946) and Milton Friedman (1912-2006). Sometimes in agreement, almost always divergent, their reading shows us how complex, different and grandiose human thought is and how to interpret the world around him.Put in the form of an "interview", let us pretend that the issues raised here are being said by them today. Without a doubt, we will be surprised to see many of their ideas with remarkable relevance, although none of the four is still alive."Let's talk", then, to Adam Smith, Marx, Keynes and Friedman.