To reason, one must wonder. Skepticism is perhaps one of the best and most rudimentary spirits in mankind. Without it we are not intelligent. We are a stray and hungry dog, and we will eat anything fed us. Skepticism is a two edged sword, both sides sharp, as pure as blue steel and just as clean.
Skepticism is, in a way, the mediating influence upon curiosity which guides it toward wisdom.
This is knowledge. This is the bedrock of scientific reference. In Latin Scientia merely means To Know. This is the world of a priori , which means the system of cross-referencing by accumulated knowledge. He doesn't have to go and observe it himself and waste time because there is an appropriate cross reference for such a phenomenon.