How early the moral sense began to form itself in our stock cannot be estimated because it must have been a very gradual process. Probably the rudiments of it appeared in the family life of the ape even before our differentiation; and the authoritative character of conscience established itself under the discipline of the hunting-pack before there was much development of mind (for dogs know what theft is), and under pressure of a public opinion that managed to express itself without language. In an original and suggestive book[80] Mr. Trotter has shown that a herd (pack, tribe or nation) necessarily approves of whatever actions are done in its interests as good or right, and disapproves of the contrary actions as bad or wrong. Confident that its beliefs and customs are good and right, the pack persecutes dissenters and nonconformists. “Good” is a relative idea. “‘The good are good warriors and hunters,’ said a Pawnee chief; whereupon the author who mentions the saying remarks that this would also be the opinion of a wolf if he could express it.”[81] Hence we may guess the principal contents of the primitive categorical imperative. The study of Ethnology and History enables us to trace the modification and enrichment of those contents under varying conditions of culture, and for the results of such study I refer to Edward Westermarck’s _Origin and Development of Moral Ideas_. (_c_) After the introduction of agriculture, the stress of natural selection was in certain directions altered. At first, indeed, most agricultural work, probably, was done by women; but in its progress it fell extensively into the hands of men; and then advantage accrued to those tribes that were capable of steady industry and prudence. The new employment decreased aggression on the principle that “had Alexander been holding the plough, he could not have run his friend Clitus through with a spear.” The sick and aged were now less an encumbrance than they had been to hunters. Those who could not endure a settled life wandered away in their old pursuits. The more aggressive clans slaughtered one another in the vendetta. Social pressure and hanging eliminated many of the more idle, improvident, dishonest and unruly, whose instincts resisted “accommodation.” The more neighbourly and co-operative tended to predominate. As civilisation intensifies, the numerous ways of getting a livelihood, which (as we have seen) derive their motive-force from the spirit of the pack, gratify that spirit under so many disguises and with so little direct personal collision, as to be compatible with a great deal of friendliness and benevolence; and co-operation, direct or indirect, steadily increases.