The equal appreciation of these two natural impulses, or the moral equivalence of self-love and love of others, is the chief and the fundamental principle of our morality. Hence the highest aim of all ethics is very simple--it is the re-establishment of "the natural equality of egoism and altruism, of the love of one's self and the love of one's neighbor." The Golden Rule says: "Do unto others as you would that they should do unto you." From this highest precept of Christianity it follows of itself that we have just as sacred duties towards ourselves as we have towards our fellows. I have explained my conception of this principle in my _Monism_, and laid down three important theses. (1) Both these concurrent impulses are natural laws, of equal importance and necessity for the preservation of the family and the society; egoism secures the self-preservation of the individual, altruism that of the species which is made up of the chain of perishable individuals. (2) The social duties which are imposed by the social structure of the associated individuals, and by means of which it secures its preservation, are merely higher evolutionary stages of the social instincts, which we find in all higher social animals (as "habits which have become hereditary"). (3) In the case of civilized man all ethics, theoretical or practical, being "a science of rules," is connected with his view of the world at large, and consequently with his religion.
From the recognition of the fundamental principle of our morality we may immediately deduce its highest precept, that noble command, which is often called the Golden Rule of morals, or, briefly, the Golden Rule. Christ repeatedly expressed it in the simple phrase: "Thou shalt love thy neighbor as thyself." Mark adds that "there is no greater commandment than this," and Matthew says: "In these two commandments is the whole law and the prophets." In this greatest and highest commandment our monistic ethics is completely at one with Christianity. We must, however, recall the historical fact that the formulation of this supreme command is not an original merit of Christ, as the majority of Christian theologians affirm and their uncritical supporters blindly accept. The Golden Rule is five hundred years older than Christ; it was laid down as the highest moral principle by many Greek and Oriental sages. Pittacus, of Mylene, one of the seven wise men of Greece, said six hundred and twenty years before Christ: "Do not that to thy neighbor that thou wouldst not suffer from him." Confucius, the great Chinese philosopher and religious founder (who rejected the idea of a personal God and of the immortality of the soul), said five hundred years B.C.: "Do to every man as thou wouldst have him do to thee; and do not to another what thou wouldst not have him do to thee. This precept only dost thou need; it is the foundation of all other commandments." Aristotle taught about the middle of the fourth century B.C.: "We must act towards others as we wish others to act towards us." In the same sense, and partly in the same words, the Golden Rule was given by Thales, Isocrates, Aristippus, Sextus, the Pythagorean, and other philosophers of classic antiquity--several centuries before Christ. From this collection it is clear that the Golden Rule had a _polyphyletic_ origin--that is, it was formulated by a number of philosophers at different times and in different places, quite independently of each other. Otherwise it must be assumed that Jesus derived it from some other Oriental source, from ancient Semitic, Indian, Chinese, or especially Buddhistic traditions, as has been proved in the case of most of the other Christian doctrines.