In the determination of present duty, it is not necessary to assume that Slavery or the Slave-Trade is positively forbidden by existing International Law. It is enough to show, that, _according to the spirit_ of that sovereign law which “sits empress, crowning good, repressing ill,” and also according to those commanding principles of justice and humanity which cannot be set at nought without shock to human nature itself, so foul a wrong as Slavery can receive no voluntary support from the Commonwealth of Nations. It is not a question of Law, but of Morality. The Rule of Law is sometimes less comprehensive than the Rule of Morality, so that the latter may positively condemn what the former silently tolerates. But within its own domain Morality cannot be less authoritative than Law. It is, indeed, nothing less than the Law of Nature, which is the Law of God. If we listen again to heathen teaching, we shall confess its truth. “Law,” says Cicero, “is the highest reason, implanted in nature, _which prescribes those things which ought to be done, and forbids the contrary_.”[118] This law is an essential part of International Law, as is also Christianity itself, and where treaties fail and usage is silent it is the only law between nations. Jurists of all ages and countries have delighted to acknowledge its authority, if it spoke only in the still, small voice of conscience. A celebrated professor of Germany in our own day, Savigny, whose name is honored by students of jurisprudence everywhere, touches upon this monitor of nations, when he declares that “there may exist between different nations _a common consciousness of right_ similar to that which engenders the positive law of particular nations.”[119] This common consciousness of right is identical with that law, which, according to Cicero, is “the highest reason, implanted in nature.” Such is the _Rule of Morality_. The Rule of Morality differs from the Rule of Law in this respect,--that the former finds support in the human conscience, the latter in the sanctions of public force. But moral power prevails with a good man as much as if it were physical. I know no different rule for a good nation than for a good man. I am sure that a good nation will not do what a good man would scorn to do.