One of the most powerful tools at our disposal is the scientific method.
1. Come up with a guess
2. Compute the consequences of your guess
3. Compare the results of experiment to the computed consequences
If careful experiment disagrees with the guess, it's wrong.
Inspired by Feynman's Messenger Lecture "Seeking New Laws", presented at Cornell University in 1964, preserved by Cal Tech. The relevant snippet of the full lecture begins at ~16:59.
