_I find myself nearly in the situation of Cicero, when he undertook to write in his own language on philosophical subjects, that, till then, had never been treated of but in Greek. He tells us that his works were said to be useless, because those who delighted in philosophy, having taken the pains to study the books written in Greek, would not afterwards think of examining his Latin ones, which were not originals; and that persons who had no taste for philosophy, would neither care for the Greek nor the Latin._ _To which he answers, that exactly the contrary would happen; that the unlearned would be allured to philosophy by the facility of reading Latin works; and that the well-informed, after studying the Greek authors, would be pleased to see how the subjects were handled in Latin._ _Cicero might with propriety speak in this manner; his superior genius and great celebrity assured him success in this untried project, but I have not the same advantages to inspire me with confidence, in a similar undertaking. I was desirous of representing philosophy in a way that was not philosophical; I have attempted to compose a book that shall neither be too abstruse for the gay, nor too amusive for the learned. But if what was said to Cicero should be repeated to me, I could not venture to answer as he did: possibly in attempting to find a middle way which would accommodate philosophy to every class, I have chosen one that will not be agreeable to any. It is very difficult to maintain a medium, and I think I shall never be inclined to make a second attempt of this nature._ _I should warn those that have some knowledge of natural philosophy, that I do not suppose this book capable of giving them any information; it will merely afford them some amusement, by presenting in a lively manner what they have already become acquainted with by dint of study. I would also inform those who are ignorant of these subjects that it has been my design to amuse and instruct them at the same time: the former will counteract my intention if they here expect improvement, and the latter, if they here only seek for entertainment._ _I need not say that of all philosophical subjects I have chosen that which is most calculated to excite curiosity: surely nothing ought to interest us more than to know how our own world is formed; and whether there be other worlds similar to it, and inhabited in the same way: but let no one be disquieted if unable to answer these enquiries; they who have time to spare may examine such subjects; many have it not in their power._