We can understand, then, why the philosophy which, when first promulgated, had tended to withdraw its adherents from participation in public life, should, when transplanted to Roman soil, have become associated with an energetic interest in politics; why it was so eagerly embraced by those noble statesmen who fought to the death in defence of their ancient liberties; how it could become the cement of a senatorial opposition under the worst Caesars; how it could be the inspiration and support of Rome’s Prime Minister during that _quinquennium Neronis_ which was the one bright episode in more than half a century of shame and terror; how, finally, it could mount the throne with Marcus Aurelius, and prove, through his example, that the world’s work might be most faithfully performed by one in whose meditations mere worldly interests occupied the smallest space. Nor can we agree with Zeller in thinking that it was the nationality, and not the philosophy, of these disciples which made them such efficient statesmen.[81] On the contrary, it seems to us that the ‘Romanism’ of these men was inseparable from their philosophy, and that they were all the more Roman because they were Stoics as well. The third great idea of Stoicism was its doctrine of humanity. Men are all children of one Father, and citizens of one State; the highest moral law is, Follow Nature, and Nature has made them to be social and to love one another; the private interest of each is, or should be, identified with the universal interest; we should live for others that we may live for ourselves; even to our enemies we should show love and not anger; the unnaturalness of passion is proved by nothing more clearly than by its anti-social and destructive tendencies. Here, also, the three great Stoics of the Roman empire—Seneca, Epictêtus, and Marcus Aurelius—rather than the founders of the school, must be our authorities;[82] whether it be because their lessons correspond to a more developed state of thought, or simply because they have been more perfectly preserved. The former explanation is, perhaps, the more generally accepted. There seems, however, good reason for believing that the idea of universal love—the highest of all philosophical ideas next to that of the universe itself—dates further back than is commonly supposed. It can hardly be due to Seneca, who had evidently far more capacity for popularising and applying the thoughts of others than for original speculation, and who on this subject expresses himself with a rhetorical fluency not usually characterising the exposition of new discoveries. The same remark applies to his illustrious successors, who, while agreeing with him in tone, do not seem to have drawn on his writings for their philosophy. It is also clear that the idea in question springs from two essentially Stoic conceptions: the objective conception of a unified world, a cosmos to which all men belong; and