Question

Why is the phrase 'endowed by their creator' found in the Declaration of Independence, concerning to some groups with regards to our country?

Answer 1

Because it presumes the existence of a Creator, i.e. God and not everybody believes in the existence of a mindful Creator. So it's a case where religious beliefs of the time and the authors are reflected in a text which applies to everyone in the Nation, not all of whom share that belief.