11.  We might say the same thing of the heavens.  With what a noise of words the sages of this world have discussed their nature!  Some have said that heaven is composed of four elements as being tangible and visible, and is made up of earth on account of its power of resistance, with fire because it is striking to the eye, with air and water on account of the mixture. This is the doctrine of Plato vide Tim.  The Combef. mss. reads not μίξις, mixture, but μέθεξις, participation.  Others have rejected this system as improbable, and introduced into the world, to form the heavens, a fifth element after their own fashioning.  There exists, they say, an æthereal body which is neither fire, air, earth, nor water, nor in one word any simple body.  These simple bodies have their own natural motion in a straight line, light bodies upwards and heavy bodies downwards; now this motion upwards and downwards is not the same as circular motion; there is the greatest possible difference between straight and circular motion.  It therefore follows that bodies whose motion is so various must vary also in their essence.  But, it is not even possible to suppose that the heavens should be formed of primitive bodies which we call elements, because the reunion of contrary forces could not produce an even and spontaneous motion, when each of the simple bodies is receiving a different impulse from nature.  Thus it is a labour to maintain composite bodies in continual movement, because it is impossible to put even a single one of their movements in accord and harmony with all those that are in discord; since what is proper to the light particle, is in warfare with that of a heavier one.  If we attempt to rise we are stopped by the weight of the terrestrial element; if we throw ourselves down we violate the igneous part of our being in dragging it down contrary to its nature.  Now this struggle of the elements effects their dissolution.  A body to which violence is done and which is placed in opposition to nature, after a short but energetic resistance, is soon dissolved into as many parts as it had elements, each of the constituent parts returning to its natural place.  It is the force of these reasons, say the inventors of the fifth kind of body for the genesis of heaven and the stars, which constrained them to reject the system of their predecessors and to have recourse to their own hypothesis. Here appears to be a reference to Arist., De Gen. Ann. ii. 3, 11, πάσης μὲν ουν ψυχῆς δύναμις ἑτέρον σώματος ἐ& 231·ικε κεκοινωνηκέναι καὶ θειοτέρου τῶν καλουμένων στοιχείων· ὡς δὲ διαφέρουσι τιμιότητι αἱ ψυχαὶ καὶ ἀτιμί& 139· ἀλλήλων οὕτω καὶ ἡ τοιαύτη διαφέρει φύσις, and again, πνεῦμα…ἀνάλογον οὖσα τῷ τῶν ἄστρων στοιχεί& 251·.  On the fifth element of Aristotle cf. Cic., Tusc. Disp. i. 10.  Aristoteles…cum quatuor illa genera principiorum erat complexus, equibus omnia orirentur, quintam quandam naturam censet esse, equa sit mens.  Aug., De Civ. Dei xxii. 11. 2, and Cudworth’s Int. Syst. (Harrison’s Ed. 1845) iii. p. 465.  Hence the word “quintessence,” for which the Dictionaries quote Howard’s Translation of Plutarch, “Aristoteles hath put…for elements foure; and for a fifth quintessence, the heavenly body which is immutable.”  Skeat s. v. points out that “the idea is older than Aristotle:  cf. the five Skt. bhútas, or elements, which were earth, air, fire, and water, and æther.  Thus the fifth essence is æther, the subtlest and highest.”  It is evident that Milton had these theories in mind when he wrote (Par. Lost, iii. 716): “Swift to their several quarters hasted then The cumbrous elements, earth, flood, air, fire; And this ethereal quintessence of heaven Flew upward, spirited with various forms, That rolled orbicular, and turned to stars Numberless.”  But yet another fine speaker arises and disperses and destroys this theory to give predominance to an idea of his own invention.