The Parliament of the Commonwealth of Australia, which is given the power to make laws for the Commonwealth by the Constitution, has two elected houses: the Senate and the House of Representatives.
There are two reasons for this division of the law-making body, the legislature, into two houses. Both reasons have a long history, pre-dating the framing of the Australian Constitution by elected conventions in the 1890s.
The first is expressed by the term bicameralism, the principle that making and changing the laws should require the consent of two different bodies. The requirement for the consent of two differently constituted assemblies is a quality control on the making of laws. It is also a safeguard against misuse of the law-making power, and, in particular, against the control of one body by a political faction not properly representative of the whole community.
Secondly, the division of the legislature into two houses allows the central legislature of the nation to reflect and secure its federal nature, that is, that it is a union of states, in which the responsibilities of government are divided between regional state legislatures representing the people of their regions and exercising regional powers, and a national legislature, representing the people of the whole country, exercising specified national powers. In such a nation, particularly a nation occupying a large geographical area, a central legislature elected by the people as a whole necessarily involves the danger that a majority within that legislature could be formed by the representatives of only one or two regions, leading to neglect of the interests of other regions and their consequent alienation from the central government. The solution to this problem is to have one house of the legislature elected by the people as a whole, representing regions in proportion to their population, and one house elected by the people voting in their separate regions, and representing those regions equally. This federal bicameral structure was invented by the framers of the Constitution of the United States of America in 1787, has been followed by federal states around the globe, and was followed by the framers of the Australian Constitution.
The Senate, bicameralism and federalism
Bases of the two Houses
Rationale of bicameralism
Rationale of federalism
The Senate and representation
Table 1: Votes and seats in elections, 1949–2010
Table 2: Party affiliations in the Senate, 1901–2010
Functions of the Senate
Composition of the Senate
Rotation of senators and terms of office
Rules and orders