material cause of evil, which consists in what is positive, and not the formal cause of it, which consists in privation, as we can say that the current is the material cause of the retardation, without being its formal cause; that is to say, is the cause of the swiftness of the vessel, without being the cause of the bounds of that swiftness. God is as little the cause of sin, as the current of the river is the cause of the retardation of the vessel.”(73) Or as Leibnitz elsewhere says, God is the author of all that is positive in our volitions, and the pravity of them arises from the necessary imperfection of the creature. We have many objections to this mode of explaining the origin of moral evil, some few of which we shall proceed to state. 1. It is a hopeless attempt to illustrate the processes of the mind by the analogies of matter. All such illustrations are better adapted to darken and confound the subject, than to throw light upon it. If we would know anything about the nature of moral evil, or its origin, we must study the subject in the light of consciousness, and in the light of consciousness alone. Dugald Stewart has conferred on Descartes the proud distinction of having been the first philosopher to teach the true method according to which the science of mind should be studied. “He laid it down as a first principle,” says Stewart, “that nothing comprehensible by the imagination can be at all subservient to the knowledge of mind; and that the sensible images involved in all our common forms of speaking concerning its operations, are to be guarded against with the most anxious care, as tending to confound in our apprehensions, two classes of phenomena, which it is of the last importance to distinguish accurately from each other.”(74) 2. The privative nature of evil, as it is called, is purely a figment of the brain; it is an invention of the schoolmen, which has no corresponding reality in nature. When Adam put forth his hand to pluck the forbidden fruit, and ate it, he committed a sinful act. But why was it sinful? Because he knew it was wrong; because his act was a voluntary and known transgression of the command of God. Now, if God had caused all that was positive in this sinful act, that is, if he had caused Adam to will to put forth his hand and eat the fruit, it is plain that he would have been the cause of his transgression. Nothing can be more chimerical, it seems to us, than this distinction between being the author of the substance of an act, and the author of its pravity. If Adam had obeyed, that is, if he had refused to eat the forbidden fruit, such an act would not have been more positive than the actual series of volitions by which he transgressed. 3. If what we call sin, arises from the necessary imperfection of the creature, as the slowness of a vessel in descending a stream arises from its cargo, how can he be to blame for it; or, in other words, how can it be moral evil at all? And, 4.