It is obvious today that the democratic political regime cannot be considered reality without taking into account political parties; it is as obvious as the phenomenon of partidocracy, expressed through the quasi-total domination of parties in politics. Such judgements prompted the title of the book . The book itself revives the term , introduced by M. Duverger in 1951, which defines the science of political parties but has not been used very much over the last decades. Its approach is explanatory and perspective alike, emphasizing the myriad of correlations surrounding the emergence, functions, types and systems of parties, on the one hand, and the electoral systems used to elect parliaments, styles of representation and executive formation on the other.