Reasoning from First Principles
A thought process that breaks down complex systems to their most basic, self-evident assumptions, and then building step-by-step from these granular pieces to a logical whole.
The concept as a philosophy stems from Aristotle and the notion of First Cause. This evolved into postulates by the Kantians, and later into postulates and axioms in mathematics. The "reasoning from first principles" concept was later popularized by Terence Irwin’s 1989 book “Aristotle’s First Principles.” (source)