John Wesley addresses the deceitfulness and wickedness of the human heart, emphasizing that it is inherently corrupt and self-deceiving. He critiques the notion that humanity is fundamentally virtuous, arguing instead that the heart is 'desperately wicked' and 'deceitful above all things,' leading to a myriad of sins and moral failures. Wesley warns against trusting in one's own heart, as it is prone to deception, and calls for reliance on God's understanding and guidance to truly know oneself. He highlights the necessity of divine grace for transformation and the importance of self-examination in the pursuit of righteousness.