Mental science has now the hardihood to maintain, Kant and the religious dogmas notwithstanding, that the moral law is completely accessible to its investigations; that true human ethics can be founded upon human nature alone; that the dogmas and commandments of pretended revelation serve only to check a progressively higher development of morals; and that the dogma which holds out promises of heaven or threats of hell in the hereafter is in its effect actually immoral, inasmuch as it seeks to regulate the moral conduct of men by purely selfish motives――by the aid of a bill of exchange upon the future life, so to speak. * * * * * In order to understand natural human ethics we must consider its natural source, that is to say, the origin of the sense of duty or social conscience. The sense of duty is, as an inclination, inborn, and therefore hereditary. It can indeed be developed or dulled by education, but it cannot be acquired; and only diseases of the brain can destroy it where it once clearly exists. What is actually inculcated or acquired, as the case may be, is not the conscience, but the object towards which it is directed, as is the case with the feeling of shame or modesty. Just as the European woman is ashamed to exhibit her bare legs, but not her face, while with the Turkish woman the reverse holds true, so the objects of the conscience, according to acquired local customs, can be absolutely opposed to one another, or at least very different in their nature. They have, however, for the most part certain features in common, which are suited to the requirements of human nature. The reason for this we shall see below. * * * * * From what does conscience, or the sense of duty, arise? First of all from a conflict between two groups of instinctive emotions allied with instinctive impulses: (1) the group of so-called egoistic feelings and impulses, directed towards self-preservation and self-gratification; and (2) the group of sympathetic or altruistic impulses directed towards the preservation and well-being of others. If I feel sympathy or love for a person, an animal, or an object, I suffer personally and feel displeasure as soon as the object of my sympathy suffers or is endangered. Hence the words compassion and sympathy (suffering with). I therefore seek to help the object of my sympathy, to save him even at the risk of personal injury; and thence the conflict arises. If my egotism triumphs I do not come to his aid, or at most only do so if I risk nothing thereby. If, on the other hand, my sense of sympathy is victorious, I sacrifice myself.