His major contribution was to recover political theory as a tradition of enquiry and regain for political science, the possibility of a critical, theoretical analysis. As different from the behaviouralists, who were beginning to make a mark in the United States of America when he was enunciating a different kind of doctrine in his lectures and seminars to his students at the London School of Economics and through his publications.
Both believe that politics has a potentiality for creative activity and should not be transformed into the dead uniformity of administration. Both are against totalitarianism, which threatens to become the predominant phenomenon of the twentieth century, and have tried to examine its intellectual and moral roots.