Edgar Morin is more than 100 years old and has produced numerous original ideas. Complex Thinking is his approach to complexity and took almost thirty years to be written. He developed it based on many other thinkers but chiefly, we argue, on Wiener's Cybernetics, von Bertalanffy's General System Theory and Shannon's Information Theory. This article describes and discusses how those latter theories have been incorporated into Morin's thought, especially in La Méthode, his magnum opus, and presents, in a comparative fashion, his pros and contras on each of them. In our conclusion, we discuss how some of Morin's criticisms of the founding theories might be unjust and also present a summary of some judgmental appraisals of Complex Thinking.