The discussion of the plurality of worlds, in the modern sense, begins with the very attractive work of Fontenelle, brought out, in its original form, in 1686, a year before Newton’s _Principia_, being a series of conversations between the Author and a witty and accomplished Marquise, as to the habitability of the several members of the solar system. The argument which followed is distinguished by many great names, those of Newton himself, Bentley, Huyghens, the Herschels, Dr. Chalmers, till it was brought to a head in the middle of the nineteenth century by Dr. Whewell and Sir David Brewster, writing respectively against and for the hypothesis. The subject was then one (as readers of Anthony Trollope will remember) upon which any one might be called upon to take a side in a London drawing-room. In more recent times interest has been concentrated upon Mars, who now possesses the distinction of having two satellites. We are only concerned to invite the reader to compare the religious argument addressed to the Stoics by Plutarch (p. 142 foll.) with the religious argument drawn by Dr. Chalmers and Sir David Brewster from the enrichment of the providential scheme for man upon our earth which would follow the conception of other earths tenanted by other beings perhaps of a higher order. But it is natural that any such speculation should begin with the moon, and in fact we find the question of her habitability discussed by Theon and by Lamprias (pp. 293-9). With the later treatises on this subject, beginning with Lucian’s witty flight of fancy, we are not concerned. But an exception must be made for the very able works of Savinien de Cyrano, known to us as Cyrano de Bergerac, whose _Histoire comique des États et Empires de la Lune_ appeared, probably, in 1650, and was followed by a similar work about the sun. Cyrano appears to be familiar with Plutarch: thus he meets in the moon the ‘daemon of Socrates’, who has also been the tutelary spirit of Epaminondas, of Cato of Utica, and of Brutus. The idea (due in the first place to Heraclitus) of being fed on smells, is worked out with much vivacity. But with so original and daring a writer, it is not quite easy to settle how much is due to any hint from others and how much to himself. A modern reader will not need to be reminded that Cyrano was not a person of whom it was wise to give an outspoken opinion in his lifetime. But I had wished to speak with nothing but respect of a man of real learning and genius, who, from whatever cause, did not bring to perfection any work worthy of himself. See, on the general subject, an Essay by the late Professor Henry J. S. Smith in _Oxford Essays_, 1855. INDEX OF PERSONS AND PLACES MENTIONED BY PLUTARCH IN THESE DIALOGUES ¶ In this Index the Greek spelling of ei (Lat. ī) has been usually retained. All dates are B. C. unless otherwise stated. The dates are often approximate and conventional.