Error is a supposition that pleasure and pain, that intelligence, substance, life, are existent in matter. Error is neither Mind nor one of Mind's faculties. Error is the contradiction of Truth. Error is a belief without understanding. Error is unreal because untrue. It is that which stemma to be and is not. If error were true, its truth would be error, and we should have a self-evident absurdity -namely, erroneous truth. Thus we should continue to lose the standard of Truth.
Mary Baker EddyIf God causes man to be sick, sickness must be good, and its opposite, health, must be evil, for all that He makes is good and will stand forever. If the transgression of God's law produces sickness, it is right to be sick; and we cannot if we would, and should not if we could, annul the decrees of wisdom. It is the transgression of a belief of mortal mind, not of a law of matter nor of divine Mind, which causes the belief of sickness. The remedy is Truth, not matter,--the truth that disease is unreal.
Mary Baker Eddy