The sermon explores the concept of conscience as a universal witness of God, building upon the previous discussion of creation. It emphasizes that conscience, though present even in the unsaved, reflects God's law written in the heart, compelling individuals to recognize right and wrong. The speaker defines conscience as what the mind allows or disallows, highlighting the importance of aligning personal standards with God's word to avoid a seared or defiled conscience, ultimately leading to a purified spirit and a deeper understanding of God's grace and mercy in a world increasingly detached from moral absolutes.