Liberal Party, a British political party that emerged in the mid-19th century as the successor to the historic Whig Party. It was the major party in opposition to the Conservatives until 1918, after which it was supplanted by the Labour Party. The Liberals continued as a minor party until 1988, when they merged with the Social Democratic Party to form what is now called the Liberal Democratic Party. Through its long history, the Liberal Party included various schools of thought, but all Liberals were united by the conviction that the source of progress lay in the free exercise of individual energy. The purpose of politics, therefore, was to create the conditions within which individual energy could thrive to the betterment of all.