First principle

First principles is a way of thinking about a problem where you start from the most basic, fundamental truths you know. Instead of relying on what other people have said or what you’ve been taught, you rely on logic and facts to build your understanding from the ground up. It can help you figure out the answers to tough problems. For example, if you want to learn why the sky is blue, you could think of first principles: you know light travels in waves, and blue light has shorter waves. When light passes through the atmosphere, the longer waves (red, orange, yellow) scatter, leaving behind the shorter waves, which is why the sky looks blue.