Liberalism is the political project which gave us the 18th century liberal revolutions of for instance, the US and France. It centers invidivual freedoms like free speech, association, and the right to own and use private property without interference from the government. It can be seen as a reaction by the land owning middle classes of the 17th and 18th centuries to the power of divine right monarchs, and is the founding principal of both the Democratic and Republican parties. It centralizes human rationality and debate of ideas as means of finding true paths to the future.

Leftism is an umbrella term which holds a few groups in it (Most notably Social democrats, Communist Socialist, and Communist Anarchist ideologies). It can be traced back through history to many times and places, but modern forms of it originate in the utopian socialism of post-revolution France. Leftism promotes the primacy of human well being and equality (or at least more equally distributed material wealth) over property rights. Generally this takes the form of support for the abolition of class society (owner class vs worker class), belief in worker-centered policy, trade unionism, worker cooperativity, and internationalism... but again, it is a big umbrella, and there is a lot of deviation from this formula. In place of rationalism and debate of ideas, Leftism generally centers material conditions and material outcomes of policy.