Andrew Sullivan on Conservatism of Doubt:

I take the Burkean and Oakeshottian view that conservatism epistemologically means an abandonment of certainty in practical life, which means a skepticism toward both radical change and toward rigid aversion to all change. Conservatives who never want change or who resist it consistently are not conservatives in this sense. They are reactionaries, hewing to an abstract ideology or theology or simply unthinking temperament where true conservatism would allow itself flexibility. Conservatives who embrace all change regardless or without due caution are obviously not conservative at all. What marks the conservative temperament, rather, is a willingness to change, sometimes radically, but never without a deep sense of  loss. Conservative change has none of the thrill of liberal “progress”. It has a tragic tincture to it, even as the conservative statesman will sometimes go further than any liberal might. Think Disraeli on suffrage, or Lincoln on war, or Burke on American independence, or Reagan on nuclear weapons.