I had a designe to comprehend all what I thought _I_ knew, before _I_ would write it, touching the nature of material things. But even as Painters, not being able equally well to represent upon a _flat_ all the severall facies of a solid body, chuse the principall of them, which they place towards the light; and shadowing the others, make them appear no more then they do to our sight: So, fearing lest _I_ should not bring into this Discourse all which was in my thoughts, _I_ onely undertook to set forth at large my conceptions touching the light; and upon that occasion to add somewhat of the Sun, and of the fix'd Stars, by reason that it proceeds almost all from thence; of the Heavens, because they transmit it; of the Planets, of the Comets, and of the Earth, because they cause it to reflect; and in particular, of all Bodies which are on the earth, whether for that they are either coloured, or transparent, or luminous; and last of all, of Man, because he is the Spectator thereof. As also, in some manner to shadow out all these things, and that _I_ might the more freely speak what _I_ judg'd, without being obliged to follow, or to refute the opinions which are received amongst the Learned, _I_ resolved to leave all this world here to their disputes, and to speak onely of what would happen in a new one, if God now created some where in those imaginary spaces matter enough to compose it, and that he diversly and without order agitated the severall parts of this matter, so as to compose a Chaos of it as confused as the Poets could feign one: and that afterwards he did nothing but lend his ordinary concurrence to Nature, and leave her to work according to the Laws he hath established.