Britain furnishes at least two prominent examples of the problem. Reference has been already made to the motive underlying the expedition of Julius Cæsar. Agricola, the greatest and the most humane of the governors of the province in the early years of its existence, found himself dragged ever farther northwards by sheer necessity of conquest. By his time, moreover, the problem had taken a more or less definite shape in men’s mind. ◆Tac. Germ. 1.◆ Tacitus, his biographer, recognized at least one side of it. “Germania,” he says, “a Sarmatis Dacisque mutuo metu aut montibus separatur”—an ethnic or physical frontier. He reports, too, a significant remark of Agricola in reference to the possibility of the conquest of Ireland: “Idque etiam adversus Britanniam profuturum, si Romana ubique arma et velut e conspectu libertas tolleretur.” The practical ethnic question was evidently in Tacitus’ time in process of becoming crystallized into a political theory. It would require too much space to recount in detail all the examples of the ethnic problem which have been conspicuous in mediæval and modern history. It has cropped up again and again within the memory of the living generation. Austria had to face it in Italy in 1859–60. She has to face it now in the Sclav provinces of the North. Denmark’s attempted solution of the problem in Schleswig-Holstein cost her those provinces in 1864. The demand for the cession of Alsace-Lorraine in 1871 would hardly have been made by Germany had not the problem in these regions presented itself to her in a seemingly favourable form. The Turkish Empire presents, and has presented, numerous examples of the problem—Servia in 1876; Bulgaria in 1878; the Greek populations of the Ægean coast at the present day. In South Africa Great Britain has been within the last year forced to solve the problem in the special phase in which it presented itself to her there. To sum up, the circumstances which give rise to the ethnic problem are, stated briefly, of the following nature— (1) The existence within but on the borders of a state of a race alien to the ruling race, but akin to the race beyond the frontier. (2) The real or fancied inferiority in respect to liberty of the aliens within the state to their kinsmen outside it. (3) The consequent setting up of two currents of feeling, one from the outside to the inside, and another from the inside to the outside of the state. These are usually coexistent, though in exceptional cases one may exist without the other. (4) The dangers to the state arising from the existence of circumstance (3). The various solutions which have been tried by different states at different periods of history have taken one of two main forms of policy— Either (1) the pushing forward of the borders by conquest to the ethnic frontier; Or (2) the denationalization of the alien race within the border.