ABSTRACT
The theory of pure and perfect competition - or atomistic competition - and the theory of monopoly are formally correct theories, in the sense that they unfold logically once their basic assumptions have been settled. Obsessed by the desire to define a producer who would be unable to have any influence on a market, the traditional theory sets a number of conditions considered as necessary for such an aim. According to the traditional theory, the situation of pure and perfect competition corresponds to an optimum because the benefit is nil - so that, therefore, no one can obtain an improvement of his or her fate without a decrease of the fate of someone else. There is in the traditional theory two symmetric situations: competition, characterised by the existence of a very large number of producers getting a profit, and monopoly or oligopoly, characterised by the existence of a small number of producers getting a 'superprofit'.
