But gradually the infant makes the painful discovery that not everything in existence can be got to serve him; there are forces which are proof against his magic spells; there are some which are hostile, and these the infant learns to regard with hatred and fear. Sometimes hatred and fear are strangely mixed with admiration and love. For example, there is a powerful being known as "father," who is sometimes good and useful, but at other times takes the attention of the supremely useful "mother," the source of food and warmth and life. So "father" is hated, and in fancy he is wished out of the way--which to the infant is the same thing as killing. Out of this grows a whole universe of fascinating mental life, which Freud calls by the name "the [OE]dipus complex"--after the legend of the Greek hero who murdered his father and committed incest with his mother, and then, when he discovered what he had done, put out his own eyes. There is a mass of legends, old as human thought, repeating this story; we cannot be sure whether they have grown out of the greeds and jealousies of this early wish-life of the infant, or whether they had their base in the fact that there was a stage in human progress in which the father really was killed off by the sons. This latter idea is discussed by Freud, in his book, "Totem and Taboo." It appears that primitive man lived in hordes, which were dominated by one old male, who kept all the women to himself, and either killed the young males, or drove them out to shift for themselves; so the young men would combine and murder their father. The forming of human society, of marriage and the family, depended upon one factor, the decision of the young victors to live and let live. The only way they could do this was to agree not to quarrel over the women of their own group, but to seek other women from other groups. This may account for what is known as "exogamy," an almost universal marriage custom of primitive man, whereby a man named Jones is barred by frightful taboos from the women named Jones, but is permitted relations with all the women named Smith.