Burke's most important contribution by far to conservative thought was his Reflections on the Revolution in France. In it he exposes the folly of radicalism and revolutionary fervour and offers an elegant defence of ancient and traditional institutions.
Burke is also a noted philosopher of Aesthetics. His A Philosophical Inquiry into the Origins of Our Ideas of the Sublime and the Beautiful is still an influence work in the field of Aesthetics today. In addition, his political speeches, writings, personal notes and correspondences are read widely by philosophers, political scientists and historians, and are sprinkled throughout with conservative thought.
As noted above, Burke is often considered to be the father of modern conservatism. He was a great conservative indeed, but to call him a founder of conservatism is inaccurate. Conservatism is more of an attitude than a philosophical system. It is sobriety in the face of fanatic enthusiasm; an inclination to preserve and not destroy, to build up and not tear down; and a cautious humility of experience against the hubris of youthful idealism. The conservative has existed beside the radical throughout the history of the human race. Edmund Burke merely captures the essence of this conservative attitude in his writings and speeches. He did not create it.