"There things we know for certain." "Oh? Name one." "The sun's going to come up tomorrow morning." "Why?" "It always has." "Does that really mean that it always will?" A faint look of consternation crossed her face. "It , won't it?" "Probably, but we can't be certain. Once you've decided that something's absolutely true, you've closed your mind on it, and a closed mind doesn't go anywhere. Question everything, Pol. That's what education's all about."