"First principles" refers to the fundamental concepts or foundational ideas on which everything else is built or understood. It is about breaking down complex ideas into their most basic elements to better understand them. Full definition
The trouble is that a natural law argument is by definition an argument from first principles of practical reason. (firstthings.com)
But we have a founder first principle for the things we invest in. (cnbc.com)
So we started with first principles — it's wise to start with a simple framework — identifying core premises from which we could build a classroom community. (edutopia.org)