which enlightenment philosopher is most directly responsible for the idea that government should be separated into multiple branches to keep each one in check?

It is written in the constitution saying all beliefs are allowed in the u.s. justice will be surved to everyone no matter what the color of that person is. and that all people are equal not matter there color is the u.s. that was a lie though because black people were still treated poorly, and there were places that was white people only such as hospitals, schools, bathroom, and more.