THERE are some matters, my most excellent Liberalis, that are investigated simply for the sake of exercising the intellect, and lie altogether outside of life; others that are a source of pleasure while the investigation is in progress, and of profit when it is finished. I shall lay the whole store of them before you; do you, as you may feel inclined, order me either to discuss them at length, or merely to present them in order to show the programme of the entertainment. But something will be gained even from those which you may order to be at once dismissed: for there is some advantage in discovering even what is not worth learning, I shall, therefore, watch the expression of your face, and, according as it guides me, deal with some questions at greater length, and pitch others headlong out of court.