To answer the above question, Koheleth cites eight different instances; four from natural, and four from moral experience. Those we might call the eight unbeatitudes of this sermon.
4 One generation passeth away, and another generation cometh: but the earth abideth for ever.
I. A generation comes, and that generation departs. But the earth the same abides.
(4.) A generation comes (i.e. proceeds; the word occurs five times in the passage). A generation sets (using exactly the same word as for the setting of the sun in the next verse), but the earth to the age abideth (i.e. remains the same as it was ‘to the age’ לעלם——this word is used in a technical sense, and occurs chapters i. 4, 10; ii. 16; iii. 11, 14; ix. 6; and xii. 5 in this book. The LXX. render by αἰών, which Bengel says is ‘sæculum præsens, mundus in sua indole cursu et censu.’ Hengstenberg observes that it is not an absolutely endless eternity, but only a future of unlimited length. Bengel’s definition, ‘the present period in its quality, course, and account,’ is exactly what the word signifies in this book. It is to be noticed that each instance of change is followed by a sentence which points out that this change is resultless. In the first, the fluctuating and fleeting generations or life-periods of man contrast with the absolute endurance of an unchanged order of things). ‘The great mill-wheel of existence only revolves for the same cogs to come uppermost again and again.’——[Hamilton, Royal Preacher.]
5 The sun also ariseth, and the sun goeth down, and [¹]hasteth to his place where he arose.
[¹] Hebrew panteth.
II. Bursts forth the sun, and sets that sun again; and wearily advancing, bursts forth as he did before.