Descartes’s cogito – I am thinking, therefore I am – is an intuitive deduction. Contrary to Transparency, certainty of I am thinking does not come easily; it’s achieved by making introspection perfectly clear through radical doubt. Scientia – rational immunity to doubt – comes with the habit of intuiting with perfect clarity that skepticism is false. (This is the second of two companion entries; the prequel is called, "Descartes's Clarity First Epistemology.").