Christian doctrine. The opening portion of the volume introduces Thomas Guthrie's sermon titled "The New Heart," which emphasizes the necessity of spiritual renewal and transformation through divine grace. He speaks to the condition of the human heart, contrasting the hardened, stony heart with a renewed, living heart that is responsive to God's will. Guthrie articulates the process of conversion, explaining how a true believer undergoes a significant change in affections and desires, ultimately aligning themselves with Christ. He illustrates these concepts with vivid metaphors and personal anecdotes, establishing a foundational principle of Christian belief: that one's heart must be transformed to truly embrace faith and the love of God. (This is an automatically generated summary.)