John Rawls

No contemporary philosopher has had more influence on political philosophy than John Rawls. With A Theory of Justice, published in 1971, Rawls both reinvigorated the then-moribund discipline and provided the theory to which nearly everything that followed was a response.
While most libertarians disagree with the core positions Rawls set out, some have argued that his ideas are in fact quite compatible with libertarian policies. Regardless of his compatibility with libertarianism, however, John Rawls is a massively influential thinker--and one any student of liberty should be familiar with.