”It is true that the devil, who cannot himself turn atheist, cannot make God's children an atheist either.
The devil must work even harder when Christ captures the castle and keeps it by the power of His grace. It is obvious that all the darts shot against Job were of this kind. When God let the devil practice his skill, why did he not tempt Job with some golden apple of profit or pleasure? Surely the high testimony God gave to His servant discouraged Satan from choosing this method; no doubt he had already tried Job's manhood and found him impenetrable. So he had no other way left but this. Now let us study three instances of this type of fiery dart and show how faith can quench them all-- temptations to atheism, blasphemy, and despair.
The fiery dart of atheism tempts us to deny God. The first of Satan's fearful temptations is his dart of atheism, an arrow, which he boldly aims at the being of God Himself. It is true that the devil, who cannot himself turn atheist, cannot make God's children an atheist either, for he has not only, in common with other men, an indelible stamp of deity in his conscience, but also such a sculpture of the divine nature in his heart as irresistibly demonstrates a holy God. It is impossible for a holy heart to be fully overcome with this temptation, because God's image within proves he has been created "after God... in righteousness and true holiness" Ephesians 4:24.
The wicked are not cleared from atheism by their naked profession of God as long as their weak thoughts fail to produce obedience to Him. "The transgression of the wicked says within my heart, that there is no fear of God before his eyes" Psalm 36:1. Thus David traces the wickedness of the sinner's life to the atheism in his heart. On the contrary, the holy life of a person saved by grace says that the fear of God is before his eyes and his belief in God is plain to see. Although a Christian can never be slain by the temptation of atheism, he may be haunted by it.”
Quoted material from, ”The Christian in Complete Armour Daily Readings in Spiritual Warfare” by Gurnall and James S Bell. http://www.moodypublishers.com/pub_productDetail.aspx?id=41823&pid=53617