William MacDonald explores the Book of Ecclesiastes, detailing Solomon's quest for life's meaning through human wisdom, ultimately concluding that life is vanity and futile without divine revelation. He emphasizes the recurring phrase 'under the sun,' which signifies the limitations of human understanding and the futility of seeking fulfillment in worldly pursuits. MacDonald highlights that while some of Solomon's observations contain truth, many are misleading, and the book serves as a cautionary tale against a life devoid of spiritual insight. He notes that true fulfillment can only be found in a relationship with God, contrasting the wisdom of man with divine wisdom. The sermon concludes with a call to remember the Creator, especially in the face of life's inevitable challenges.