Piper advocates Christian hedonism and teaches that "God is most glorified in us when we are most satisfied in Him" and that God's highest pursuit ("his glory") and man's deepest and most durable happiness come together in one pursuit—namely, the pursuit of joy in God. Piper holds to a complementarian view of gender roles. This view says that the Bible teaches that a husband is called to lovingly lead, protect and provide for his wife and family, and that the wife should affirm and submit to her husband's leadership. He also says that the Bible teaches that men are to bear the primary responsibility to lead the church and that therefore only men should be elders. Piper, along with Wayne Grudem, was co-editor of one of the books in this area, called "Recovering Biblical Manhood and Womanhood". One of the chapters has been reprinted several times as an independent short book called "What's the Difference?" Piper's soteriology is Calvinist and his ecclesiology is Baptist. He affirms the distinctively Calvinist doctrine of double predestination, which includes "unconditional reprobation" or damnation as a corollary to the Augustinian doctrine of unconditional election, and he subscribes to the Leibnizian view that God decreed this universe to be the best of all possible universes. Piper believes in justification by faith alone apart from works of man, and his teachings emphasize the need for the active and inevitable perseverance of the believer in faith, sanctification, and enduring sufferings, which he believes is evidence of God's saving grace. According to Piper, a once-professing Christian who does not faithfully persevere until the end demonstrates that he was mistaken about his election and was never a true believer in the first place. Piper espouses a brand of creationism known as "historical creationism", and credits John Sailhamer's book "Genesis Unbound" to explaining the view. "Historical creationism" states that God created the universe, planet Earth, and many creatures and things within Earth itself over the course of an indefinite time period before the first day of the week of Genesis 1, and that the days of the creation week were God changing a desolate piece of land into the blessed region of Eden, where God would bring Adam and Eve into existence and place them within it on the sixth day. "In verse 1," Piper said, "'In the beginning he made the heavens and the earth,' he makes everything.