thoughts!_[99] We are now, however, about to people the Fixed Stars. The only proof that they are the centres of planetary systems, resides in the assumption that these Stars are _like the Sun_; and as resembling him in their nature and qualities, so having the same offices and appendages:—independent sources of light, and thence probably of heat; therefore having attendant planets, to which they may impart such light and heat,—and these planets’ inhabitants living under and enjoying those benign influences. Everything here depends on this proposition, that the Stars are like the Sun; and it becomes essential to examine what evidence we have of the exactness of their likeness.[100] In the Preface to his Second Edition, the Essayist, whose scientific knowledge few will venture to impugn, boldly asserts that “man’s knowledge of the physical properties of the luminaries which he discerns in the skies, is, even now, _almost nothing_;” and “such being the state of our knowledge, as bearing on the doctrine of the plurality of worlds, the time appeared to be not inopportune for a calm discussion of the question,—upon which, accordingly,” he adds, “I have ventured in the following pages.” In the same Preface he has ably condensed into a single paragraph his views on the nature and extent of our present knowledge on the subject of the Fixed Stars.[101] In the opening of the chapter devoted to this subject (ch. viii.), he admits “the special evidence,” as to the probability of these stars containing, in themselves, or in accompanying planets, inhabitants of any kind, “is, indeed, slight, _either way_.”