Final answer:
Egalitarianism is the ethical principle that argues for equal status and moral worth among individuals, and Rawls's Difference Principle refines this concept by stating inequalities must benefit society's least advantaged.
Step-by-step explanation:
The ethical principle that asserts that equals should be treated the same is known as egalitarianism. This principle revolves around the idea that individuals should enjoy equal status and moral worth, and that legitimacies of a government should mirror these values. A more nuanced version of egalitarianism is expressed through John Rawls's Difference Principle, which argues that social and economic inequalities must be justified by benefiting the least advantaged in society and that positions associated with them be open to all under fair equality of opportunity.