For Richard Rose 'party cohesion is a means to an end: it ensures the parliamentary endorsement of government measures' (Rose 1983 : 283). Parties thus perform a highly important systemic level function in contributing to the formation and, just as important, the maintenance of government. Indeed, it is enormously hard to imagine legislatures without parties (Sinclair 1998 : 24). Still, as functional as parties are for parliamentary systems, this does not necessarily explain how parties are functional from the point of view of individual parliamentarians. The fact that parties may perform useful functions inside a legislature does not necessarily explain why individual legislators remain members of the same legislative bloc throughout their careers. And, as the bulk of current writings on legislatures reminds us, it is this individual or micro-level functionality that is all important.
In what follows we look at two broad arguments that help to explain the presence of legislative parties from the point of view of individual legislators. One theory looks to the role of elections and election fighting as the main source of glue that bonds legislators together; the other looks to the need for collective action inside the legislative chamber. This latter argument has become especially influential of late. Influential but not wholly persuasive; and in the last section of the chapter we offer an account in which party organizations provide an important adhesive force and we argue that while 'parties in the electorate' may not provide a sufficient explanation for 'party governmen', 'parties as organizations' may do so.
The chapter then examines evidence that relates to the institutional structures and incentives that benefits political parties within the legislative arena. We examine the formal rules of procedures across the national parliaments in most advanced industrial democracies. Then, we examine the parties' influence on the legislative process and legislative decision-making. The results provide a basis for discussing how in the legislature have reacted to the patterns of change discussed in other chapters of this volume.