Apart from the assertion of his cardinal principle with which we are familiar, namely, that since our Sun has an inhabited planet, all others must; and also that all planets must be inhabited;—the argumentative value of these two chapters seems to lie in this that they annihilate one of the Essayist’s points of _unlikeness_ between our Sun and other Fixed Stars, inasmuch as it, together with so many of them, is one of a binary system: wherefore what is true of it, is true of them, _et vice versa_. He bases this proposition, viz., that our Sun is one of a binary system, on “high probability,” from “the motion of our own system round a distant centre.”[109] The great truth of this motion, he says the Essayist “has completely misrepresented, foreseeing its influence on the mind as an argument for more worlds than one.”[110] What the Essayist had said on the subject, was this:[111] he speaks of “the _attempt_ to show that the Sun, carrying with it the whole solar system, is in motion; and the further attempt to show the direction of that motion;—and again, the hypothesis that the Sun itself revolves round some distant object in space.” These minute inquiries and bold conjectures, he says, “cannot throw any light on the question, whether any part besides the earth _be inhabited_: any more than the investigation of the movements of the ocean and their laws can prove or disprove the existence of _marine plants and animals_. They do not, on that account, cease to be important and interesting objects of speculation, but they do not belong to our subject.” As to the Sun’s motion, we are bound to say, that the Astronomer Royal has recently declared that “every astronomer who has examined the matter carefully, has come to the conclusion of Sir William Herschell, that the whole solar system is moving towards a point in the constellation Hercules.”[112] Before quitting this part of the subject, we may state that the Essayist, in his second Preface,[113] points out the insecure character of astronomical calculations as to the amount of absolute light ascribed to some of the fixed stars. It has been estimated that the illuminating power of _Alpha_ Centauri is nearly double that of the Sun, placed at that distance, which is two hundred thousand times as far off as is the Sun; but Sir John Herschell will not concur in more of the calculation than attributes to the star the emission of _more_ light than our Sun. Surely the critical and precarious character of such calculations should not be lost sight of by candid inquirers, but incline them to scan somewhat closely any pretensions tinctured by astronomic dogmatism.