Under the conditions of civilized life the primitive expression of pugnacity in physical combat has been outlawed and made unnecessary by law and custom. Individuals are prevented by the fear of punishment, besides their early training and habits, from settling disputes by physical force. But as the instinct itself remains strong, it must find some other outlet. This it secures in more refined forms of rivalry, in business and sport, or, all through human history, in fighting between groups, from the squabbling and perpetual raids and killings, and the extermination of whole villages and tribes in Central Borneo, to the wars between nations throughout European history. PUGNACITY A MENACE WHEN UNCONTROLLED. The strength and persistency of this human tendency, when uncontrolled or when fostered between groups, make it a very serious menace. Like all the other instincts, and more than most, it is frustrated and continually checked in the normal peace-time pursuits of contemporary civilization. Participation, imaginative at least, in a great collective combat undoubtedly holds some fascination for the citizens of modern industrial society, despite the large-scale horror which war is in itself, and the desolation it leaves in its wake. During peace the fighting instinct for most men receives satisfaction on a small scale, sometimes in nothing more important than small bickerings and peevishness, or in seeing at first hand or on the ticker a championship prize-fight. The pessimism which many writers have expressed at the possibility of perpetual peace rests in part on their perception of the easy excitability and deep persistence of this impulse, especially among the vigorous and young. Not only may the fighting instinct be aroused by the possibility of international wars, but it may be used by fomenters and agitators to add a sense of intense pugnacity and violent anger to the genuine friction that does exist between conflicting interests in the same society. The theory of a "class war" possibly finds its appeal for many minds as much in its picturesque stimulation of their instincts of pugnacity as in the logic of its economics.