Since the nineteen-fifties, the American political scientist Robert Dahl (born in 1915) has been one of the most prominent democracy theorists in the world. In the book Politics, Economics, and Welfare, he and his colleague Charles E. Lindblom in 1953 introduced the notion of polyarchy as a denomination for the incomplete democracies of the Western world. Linguistically speaking, this notion was formed in connection with the ones already existing in the philosopher Aristotle's (384-322 B.C.) comparative teachings on government. Later, it has become apparent that the notion of polyarchy has already been in use by other authors, such as Johannes Althusius (1614) and Sir Ernest Barker (1947).Robert Dahl has been active at Yale University (in New Haven, Connecticut, USA), and is regarded as one of the foremost representatives of the political-science discipline known as pluralism.