John Nelson Darby emphasizes that Christ, as the Searcher of Hearts, reveals the true state of humanity, showing that there is no inherent goodness in man apart from God. He illustrates how Christ's probing of our hearts leads to a deeper understanding of our need for grace and the necessity of taking up the cross to follow Him. Darby highlights the importance of self-examination and the dangers of allowing worldly affections to distract us from our relationship with God. He encourages believers to trust in Christ's love and to recognize that true life is found in being dead to the world and alive to God. Ultimately, the sermon calls for a heart fully surrendered to Christ, willing to follow Him despite the challenges of the world.