“I know very little with anything approaching certainty. I know that I was born, that I exist, and that I will die. For the most part, I can trust my brain's interpretation of the data presented to my senses: this is a rose, that is a car, she is my wife. I do not doubt the reality of the thoughts and emotions and impulses I experience in response to these things. . . . Yet apart from these primary perceptions, intuitions, inferences, and bits of information, the views that I hold about the things that really matter to me--meaning, truth, happiness, goodness, beauty--are finely woven tissues of belief and opinion.”