A philosophy is a set of beliefs. In the case of liberalism, though specific liberals may be all over the map in terms of what they consider the most important

A philosophy is a set of beliefs. In the case of liberalism, though specific liberals may be all over the map in terms of what they consider the most important of these, they all share a common belief in liberty, consent of the governed, and equality under the law. Liberals, by and large, are happy with slow progress towards a better world. They get very suspicious when people start advocating plans of action that don't fit with the platform. Leftists are interested in an ideal society, according to leftist political thought that's generally thought to have originated with Marx. Though individuals may have different ideals, they're all organized around certain lines. The ideal communist society and the ideal anarchist society both lie in a direction we call 'left', and the same sets of political tactics move in that direction. Leftists are more interested in the direction than in the philosophy. The big political divide in the 17-1800s was monarchy over republic. Republics won that fight, now we're in the tail end of the fight between conservatism and progressivism. Now the left has to decide just what sort of course to chart to get to a better world.