My aim and object must, I think, be very obvious, and you must be conscious how earnestly I desire in arguing not to score a victory on the strength of plausible lies, but by careful inquiry to point out the truth. And I am quite sure that you are so disposed. So please, therefore, without hesitation use such means as you consider best for the discovery of the truth, for by so doing you will profit not yourself only but me also, by showing me my ignorance. It seems clear to me that evil has a substantial existence, for I never see what is evil apart from substances.