"it has been a period of unexampled change, -- swift, varied, profound and extensive beyond example. And it follows of necessity that the principles of conduct which were approved and stabilized in the eighteenth century, under the driving exigencies of that age, have not altogether escaped the complications of changing circumstances. They have at least come in for some shrewd interpretation in the course of the nineteenth century. There have been refinements of definition, extensions of application, scrutiny and exposition of implications, as new exigencies have arisen and the established canons have been required to cover unforeseen contingencies; but it has all been done with the explicit reservation that no material innovation shall be allowed to touch the legacy of modern principles handed down from the eighteenth century, and that the vital system of Natural Rights installed in the eighteenth century must not be deranged at any point or at any cost."