Charles Finney addresses the dangers of Antinomianism and legalism in his sermon 'Letters on Revival--No. 4,' emphasizing that both extremes deviate from true Christianity. He explains that Antinomians, having rejected self-righteous efforts, often fall into spiritual indolence, mistaking passive faith for true faith, which should be active and energizing. Finney argues that true faith is characterized by a deep sympathy with Christ and a commitment to benevolence, leading to active participation in the mission of the church. He warns against following mere feelings instead of being guided by the Word of God, urging believers to find balance in their spiritual lives. Ultimately, he calls for a revival that embodies the true spirit of Christianity, avoiding both extremes.