When I said skeptic was referring to something like a critical examination of the evidence. The scientist should not accept something on faith alone. We judge something on the merits of the evidence. Our theories are put on trial and the experiment is our test. A religious person might say that we are letting God decide our beliefs.

I think we need more than DesCartes "cogito ergo sum." You have to start with something and this is the world around us. His method of doubt is a little too extreme. It leaves us in a world of our own.

Re the "the illusion of perception": Are you referring to something like Kant's noumena, where we have an imperfect knowledge of reality? Didn't Aristotle say something similar when referring to the substratum?

I didn't realize it when I posted my last message that today is the Epiphany. Ancient astronomy may have been more advanced that most people realize. Time has a tendency to filter the evidence. There were some very intellegent people back in the Classical Greek period. Our evidence is not direct. We might get a better picture if we enhance the evidence a little.

If I recall my history correctly, the Epiphany has as a partial basis an ancient Egyptian feast which celebrated a closeness to God. The time of the feast was near Earth's perihelion. Were the Egyptian astronomers that smart? I refer you to Aristarchos and others of the Greek period. The Greeks of the classical period certainly had contact with Egypt and there is evidence that some of the aristocracy were educated by Egyptian priests.