So varied and complex is the world of games that there are many ways in which a study of it can be approached. Psychology, sociology, anecdotal history, pedagogy, and mathematics all share a domain whose unity ends by ceasing any longer to be perceptible. Works like Homo ludens by Huizinga, Jeu de l'enfant by Jean Chateau, and Theory of Games and Economic Behavior by J. von Neumann and O. Morgenstern are not addressed to the same readers, nor do they appear to deal with the same subject. Ultimately, this question arises: How much does one profit from the facilities or contingencies of vocabulary by continuing to act as though such different and almost incompatible inquiries are fundamentally concerned with a same specific activity? It is doubtful whether common characteristics permit one to define this specific activity and consequently whether it can legitimately constitute the object of a comprehensive study.