A.W. Tozer emphasizes that sin originates in the mind, which encompasses not just intellect but the entire personality, including will, emotions, and moral responses. He points out that the carnal mind is in opposition to God and cannot adhere to His law. Tozer references Genesis 6:5 to illustrate that the wickedness of humanity is rooted in the heart, where evil desires and intentions dwell. He urges listeners to recognize that true sin is a matter of the heart, affecting every aspect of a person's being. The sermon calls for introspection and a deeper understanding of the heart's role in our relationship with God.