Consider the following principles of justice theorized by renowned philosophers:

1. John Rawls' Principles of Justice,

2. Robert Nozick's Entitlement Theory,

3. Amartya Sen's Idea of Justice,

4. Karl Marx's Classless Society.

Which philosophical approach best represents the concept of justice as fairness, emphasizing that societal resources should be distributed equally unless an unequal distribution would be to everyone's advantage?