All the stars consist of the same elements, since water cannot subsist without earth, nor fire without water; but in some stars the aqueous element predominates (planets), in others the igneous (suns). From sameness of appearance and of effects (_accidents_) we may infer sameness of substance. It is clear therefore to Bruno that moon, planets, stars, are all of precisely the same substance as the earth. It is unnecessary to point out by how long a period this brilliant philosophical faith preceded the slower if surer march of science. The great worlds of the universe are of two kinds--the suns, in which fire is the predominating element, and from which light is diffused; and the earths or planets, in which water predominates and which reflects light. To the first class belong the so-called fixed stars, from which our sun would appear no larger and no brighter than they appear to us; to the second belong the moon, Mercury, and other planets, all in one and the same ethereal space, suspended in free air and balanced by their own weight as is our earth. In all are seas and woods, rivers, men, cattle, reptiles, birds, fishes, as on the earth, and in all the same continuous changes occur.[361] No one is in the centre of the universe rather than another, for about all equally extends immeasurable space with its innumerable stars. Of these "first bodies" one kind could not exist without the other, for it is by the concourse of contraries and opposites that nature provides for movement, life, and growth in things. About each of the scintillating stars, or suns, which we see, there must circle planets which are for the most part invisible to us, but which _may_ become visible.[362] In the same way, both on account of the smallness of their bodies, and especially on that of the less intensity of reflected light in comparison with light of original force, the planets which are about our fixed star, the sun, would not be seen from any of the others. The discovery in the last half-century of what is almost certainly a satellite of Sirius confirms in this also Bruno's "anticipation of nature." Another of these was his theory of comets,[363] which he held to be of the same nature as planets, and to move in similar orbits. He believed also that there were other solar planets which never appeared to us because their position in the heavens precluded their reflecting any of the sun's rays to us:--a belief to which the reported eclipses of the sun by occult bodies has given some support. The shape of the comet, with its appendages, was only apparent, Bruno said, and was due to the angle made by the light reflected from its surface. In another reference, however, he compares it with the oblique reflection of light from a mirror, or from the surface of water; it is the watery matter, the vapours which are drawn out by the warmth of the sun, that give the unusual reflection.[364] This shows how nearly he approached the modern theory.