In reality, cleanthes, continued he, the modern system of astronomy is now so much received by all inquirers, and has become so essential a part even of our earliest education, that we are not commonly very scrupulous in examining the reasons upon which it is founded.  It is now become a matter of mere curiosity to study the first writers on that subject, who had the full force of prejudice to encounter, and were obliged to turn their arguments on every side in order to render them popular and convincing.  But if we peruse GALILEO’s famous Dialogues concerning the system of the world, we shall find, that that great genius, one of the sublimest that ever existed, first bent all his endeavours to prove, that there was no foundation for the distinction commonly made between elementary and celestial substances.  The schools, proceeding from the illusions of sense, had carried this distinction very far; and had established the latter substances to be ingenerable, incorruptible, unalterable, impassable; and had assigned all the opposite qualities to the former.  But Galileo, beginning with the moon, proved its similarity in every particular to the earth; its convex figure, its natural darkness when not illuminated, its density, its distinction into solid and liquid, the variations of its phases, the mutual illuminations of the earth and moon, their mutual eclipses, the inequalities of the lunar surface, &c.  After many instances of this kind, with regard to all the planets, men plainly saw that these bodies became proper objects of experience; and that the similarity of their nature enabled us to extend the same arguments and phenomena from one to the other.

In this cautious proceeding of the astronomers, you may read your own condemnation, cleanthes; or rather may see, that the subject in which you are engaged exceeds all human reason and inquiry.  Can you pretend to show any such similarity between the fabric of a house, and the generation of a universe?  Have you ever seen nature in any such situation as resembles the first arrangement of the elements?  Have worlds ever been formed under your eye; and have you had leisure to observe the whole progress of the phenomenon, from the first appearance of order to its final consummation?  If you have, then cite your experience, and deliver your theory.

PART 3

How the most absurd argument, replied cleanthes, in the hands of a man of ingenuity and invention, may acquire an air of probability!  Are you not aware, Philo, that it became necessary for Copernicus and his first disciples to prove the similarity of the terrestrial and celestial matter; because several philosophers, blinded by old systems, and supported by some sensible appearances, had denied this similarity? but that it is by no means necessary, that Theists should prove the similarity of the works of Nature to those of Art; because this similarity is self-evident