The psychological explanation of barter has brought forth the theory of the marginal utility, its greatest merit. According to this theory, the subjective valuation of any economic good decreases in proportion to the number of objects of the same kind possessed by the same owner. When even two proprietors meet, each having a number of similar articles, they will gladly barter, provided political means are barred, i. e., if both parts are apparently equally strong and well-armed, or in the very early stage, are within the sacred circle of relationship. By barter, each one receives property of very high subjective value, in place of property of very low subjective value, so that both parties are gainers in the transaction. The desire of primitive people for bartering must be stronger than that of cultured ones. For at this stage man does not value his own goods, but covets the things belonging to strangers, and is hardly affected by calculated economic considerations. On the other hand, we must not forget that there are primitive peoples for whom barter has no attraction whatever. “Cook tells of tribes in Polynesia, with whom no intercourse was possible, since presents made absolutely no impression on them, and were afterward thrown away; everything shown them they regarded with indifference, and with no desire to own it, while with their own things they would not part; in fact, they had no conception of either trade or barter.”[58] So Westermarck is of the opinion that “barter and traffic are comparatively late inventions.” In this he stands in opposition to Peschel, who would have it that man in the earliest known stage of development engaged in barter. Westermarck states that there is no proof “that the cave-dwellers of Périgord from the reindeer period obtained their rock-crystals, their shells from the Atlantic, and the horns of the Saiga antelope from (modern) Poland by way of barter.”[59] In spite of these exceptions, which admit other explanations--perhaps the natives feared sorcery--the history of primitive peoples shows that the desire to trade and barter is a universal human characteristic. It can, however, take effect only when these primitive men on meeting with strangers are offered new enticing objects, since in the immediate circle of their own blood kinsmen every one has the same kinds of property, and in their natural communism, on the average about the same amount. Yet even then, barter, the beginning of all regular trading, can take place only when the meeting with foreigners is a peaceable one. But is there any possibility for peaceable meeting with foreigners? Is not primitive man, through his entire life, and especially at the period when barter begins, still under the apprehension that every one of a different horde is an enemy to be feared as the wolf?