Charles Finney emphasizes that a willing mind is essential for understanding God's truth, as highlighted in John 7:17. He explains that God's promises reveal the principles of His governance and that a genuine willingness to do His will involves implicit trust, love, and a desire for truth. Finney argues that this state of mind is crucial for honest inquiry and embracing truth, and neglecting the means of knowledge can tempt God. Ultimately, he encourages believers to seek a candid state of mind to fully know and do God's will, urging them to open their hearts to divine guidance.