This principle is common to every system of civilized jurisprudence; but it has been nowhere expressed with more force than in the maxims of the Common Law and the decisions of its courts. It entered into the remarkable argument of Granville Sharp, which preceded the judgment extorted from Lord Mansfield, and led him to exclaim, in words strictly applicable to the Constitution of the United States, “The word _slaves_, or anything that can justify the enslaving of others, is not to be found, God be thanked,” in the British Constitution.[316] It entered into the judgment pronounced at last by Lord Mansfield, under the benevolent pressure of Granville Sharp, in the renowned Somerset case, where this great magistrate grandly declared that Slavery could not exist in England. His words cannot be too often quoted as an illustration of the true rule of interpretation. “The state of Slavery,” he said, “is of such a nature, that it is incapable of being introduced on any reasons moral or political, _but only by positive law_.… It is so odious, that nothing can be suffered to support it _but positive law_.”[317] Therefore the authority for Slavery cannot be derived from any words of doubtful import. Such words are not “positive.” And clearly, by the same rule, _if the words are susceptible of two different significations, that must be adopted which is hostile to Slavery_. This same cardinal principle, thus announced by the Chief Justice of England, has been echoed by the Chief Justice of the United States, being none other than Marshall, speaking for our own Supreme Court, when he said, “_Where rights are infringed_, … the legislative intention must be expressed with _irresistible clearness_ to induce a court of justice to suppose a design to effect such objects.”[318] In a clause capable of _two meanings_ there can be no such “irresistible clearness” as would justify an infringement of human rights.