Augustine's famous saying: man can't be satisfied, and only in God can he rest in peace. But with God, life becomes complete and meaningful, and generate's life is full of hope from God. The missionary ended the book with a positive thought: it is the duty of human beings to fear God and keep his commandments.
Historical background
The author of Ecclesiastes calls himself "the preacher", hence the name. The original meaning of "preacher" is "convener of the meeting", which is translated by some scholars as "president", probably because he often convenes a group of people to attend lectures. Traditionally, the author is considered as Solomon (King of Jerusalem), because he is a descendant of David and enjoys all the splendor and wisdom.
However, the negative view of life in the book is not consistent with Solomon's remarks in his heyday, so the tradition holds that this is Solomon's reflection and repentance after leaving God for a period of time in his later years.
This book is Solomon's heartfelt words, the testimony of his personal experience and his heartfelt advice. He used his past failures to earnestly warn the world that the empty life under the sun is because people left the true God above the sun.