This chapter examines some of the important features of the Anglo-Australian legal system. It looks at the values that constitute liberalism, the concepts of the rule of law and equality, the relationship between law and morality, the separation of powers, responsible government and federalism. The dominant political philosophy in Western democracies such as the United Kingdom, the United States and Australia is liberalism. Liberal political philosophy is a product of the Enlightenment or ‘age of reason’, a period in the European history of ideas which spanned the late seventeenth and eighteenth centuries. The approaching centenary of Federation has focused attention on the levels of political philosophy and constitutional theory. The chapter considers various justifications for the standard form of the doctrine of the separation of powers, which distinguishes between executive, legislative and judicial power. Any revision of the federal system or broader rewriting of the Constitution should involve a rethinking and re-evaluation of its underlying philosophical principles and values.