When Newton first discovered the property of attraction, and settled its laws, he found it served very well to explain several of the most remarkable phenomena in nature; but yet with reference to the general system of things, he could consider attraction but as an effect, whose cause at that time he did not attempt to trace. But when he afterwards began to account for it by a subtle elastic aether, this great man (if in so great a man it be not impious to discover anything like a blemish) seemed to have quitted his usual cautious manner of philosophising: since, perhaps, allowing all that has been advanced on this subject to be sufficiently proved, I think it leaves us with as many difficulties as it found us. That great chain of causes, which linking one to another even to the throne of God himself, can never be unravelled by any industry of ours. When we go but one step beyond the immediate sensible qualities of things, we go out of our depth. All we do after is but a faint struggle, that shows we are in an element which does not belong to us.