In a book called Symbolism, Its Meaning and Effect, Whitehead points out that perception is usually a matter of symbols, just like language; I say I see a book when I actually see a red oblong. The Transactionists (who have been influenced by Whitehead rather than Husserl) take this one stage further, and point out that when I 'perceive' something, I am actually making a bet with myself that what I perceive is what I think it is. In order to act and live at all, I have to make these bets; I cannot afford to make absolutely certain that things are what I think they are. But this means that we should not take our perceptions at face value, any more than Nietzsche was willing to take philosophy at its face value; we must allow for prejudice and distortion.