In 7:1—12:12 we have the writer's searching and testing.
The writer searched and tested all things of the fallen human life under the sun (7:23-29; 8:9, 16; 12:9-10).
All the things under the sun, regardless of the kind of persons involved, wise or foolish, diligent or lazy, rich or poor, old or young, high or low, righteous or wicked, good or sinful, clean or unclean, and regardless of how they were born, how they worked, how they died, and how their end was, all are vanity of vanities (7:6, 15; 8:10, 14; 9:9; 11:8, 10; 12:8).
Proverbs, words of wisdom, were produced out of the writer's searching and testing (7:1-9, 11-12, 14-17; 8:1b, 5b, 8; 9:4b, 7-12, 16-18; 10:1-2, 4b, 8-14a, 18-20; 11:1, 3-8; 12:11, 12b). All these proverbs are good for building up the character of one who lives a better human life, but they do not have the function to afford the growth in the divine life for the building up of the Body of Christ. Yet, for the building up of the Body of Christ there is the need of a proper character, not by self-cultivation but by the Spirit's anointing under the work of the cross of Christ with the rich elements of Christ (Gal. 5:16; 2:20; Phil. 1:19-21).
The writer searched and tested what God is to man.
God created man, so God is the Sovereign over man (Eccl. 7:29; 12:1).