The sun is in perpetual motion, sometimes arising, and sometimes setting, and then arising again, and so constantly repeating its courses in all succeeding days, and years, and ages; and the like he observes concerning the winds and rivers, Ecclesiastes 1:6,7. And the design of these similitudes seems to be, either,
1. That by representing the constant changes and restless motions of these particular things he might intimate that it is so with all other earthly things; and therefore no man can expect satisfaction from them. Or,
2. That by comparing the sun, and wind, and rivers, as, Ecclesiastes 1:4, he compared the earth with man, he might show that man, considered as mortal, is in a more unhappy condition than these things, because when the earth abides, man goes; and when the sun sets, he riseth again; and so the wind and rivers return to their former place and state, but man, when once he dies, he never returns again to this life; of which comparison see Job 14:7,12. Or,
3. To show the vanity of all worldly things, and that man's mind can never be satisfied with them, because there is nothing in the world but a constant repetition of the same things, which is so irksome a thing, that the consideration thereof hath made some persons weary of their lives; and there is no new thing under the sun, as is added in the foot of the account, Ecclesiastes 1:9, which seems to me to be given as a key to understand the meaning of the foregoing passages. And this is manifest and certain from experience, that the things of this world are so narrow, and the mind of man so vast, that there must be something new to satisfy the mind; and even delightful things, by too frequent repetition or long continuance, are so far from yielding satisfaction, that they grow tedious and troublesome.