Critical thinking entails not automatically accepting claims without credible supporting evidence, and subjecting such evidence as is presented to exceptional scrutiny proportionate to the claim. Basically a triple whammy of ECREE, the Holmesian Maxim and Occam's Razor.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'