A mistake is the acceptance of an object to be different than what it is or the acceptance of false knowledge. For example, one may see a rope in the dark and think it to be a serpent, or one may see a glittering oyster shell and think it to be gold. These are mistakes. Similarly, an illusion is a misunderstanding that arises from inattention while hearing, and cheating is the transmission of such defective knowledge to others. Materialistic scientists and philosophers generally use such words as "maybe" and "perhaps" because they do not have actual knowledge of complete facts. Therefore their instructing others is an example of cheating. The final defect of the materialistic person is his inefficient senses. Although our eyes, for example, have the power to see, they cannot see that which is situated at a distance, nor can they see the eyelid, which is the object nearest to the eye. To our untrained eyes the sun appears to be just like a plate, and to the eyes of one who is suffering from jaundice everything appears to be yellow. Therefore we cannot rely on the knowledge acquired through such imperfect eyes. The ears are equally imperfect. We cannot hear a sound vibrated a long distance away unless we put a telephone to our ear. Similarly, if we analyze all our senses in this way, we will find them all to be imperfect. Therefore it is useless to acquire knowledge through the senses. The Vedic process is to hear from authority. In the Bhagavad-gita (4.2) the Lord says, evam parampara-praptam imam rajarsayo viduh: "The supreme science was thus received through the chain of disciplic succession, and the saintly kings understood it in that way." We have to hear not from a telephone but from an authorized person, for it is he who has real knowledge.