The dominant ideological foundation of our constitutional system (and that of other
countries that were once part of the British Empire, such as Canada, Australia,
and Great Britain itself) is known as classical liberalism. This ideology is very
clearly expressed in John Locke’s Second Treatise of Civil Government (1690).
Among the many beliefs of liberalism is that power derives from the consent of the
governed—that is, the people themselves. The people, and not royalty or the state,
are therefore sovereign. Thus, when policy advocates seek to induce the government
to make policy (by taking an action or refusing to do so), or when government
actively engages in actions these advocates support, one can make a claim that the
government does so in the public interest. Indeed, many states have groups called
public interest research groups, or PIRGs, which promote their interpretation of
the public interest.