Charles Finney addresses the concept of 'Evil Thinking' in his sermon, emphasizing that true charity, or love, does not harbor evil thoughts about others. He explains that thinking evil includes forming unjust opinions, being envious, suspicious, or malicious, and dwelling on the faults of others. Finney highlights that a charitable mind is characterized by kindness, a lack of revenge, and a tendency to see the good in others, while evil thinking leads to unhappiness and discontent. He warns that evil thinkers not only harm themselves but also negatively impact their families and communities. Ultimately, he calls for a transformation of the mind to align with the principles of love and charity as taught in Scripture.