Charles Finney emphasizes the necessity of self-examination for Christians to understand their true moral character in the eyes of God. He argues that uncertainty about one's spiritual state leads to a lack of peace and that individuals must actively engage with their faith to discern their standing as either saints or sinners. Finney warns against the dangers of self-deception and the importance of focusing on God and His standards to gain clarity about one's feelings towards sin and salvation. He encourages believers to take action in their faith rather than waiting for feelings to come, asserting that true emotions arise from engaging with the realities of faith and the world around them.