In the book God’s Passion for His Glory: Living the Vision of Jonathan Edwards, Piper writes about the present state of evangelicalism:
I resonate with the lament of Os Guinness and David Wells that evangelicalism today is basking briefly in the sunlight of hollow success. Evangelical industries of television and radio and publishing and music recordings, as well as hundreds of growing mega-churches and some highly visible public figures and political movements, give outward impressions of vitality and strength. But both Wells and Guinness, in their own ways, have called attention to the hollowing out of evangelicalism from within.
In other words, the strong timber of the tree of evangelicalism has historically been the great doctrines of the Bible—God’s glorious perfections, man’s fallen nature, the wonders of redemptive history, the magniﬁcent work of redemption in Christ, the saving and sanctifying work of grace in the soul, the great mission of the church in conﬂict with the world and the ﬂesh and the devil, and the greatness of our hope of everlasting joy at God’s right hand. These things once deﬁned us and were the strong ﬁber and timber beneath the fragile leaves and fruit of our religious experiences. But this is the case less and less. And that is why the waving leaves of success and the sweet fruit of prosperity are not as auspicious to David Wells and Os Guinness as they are to many. It is a hollow triumph, and the tree is getting weaker and weaker while the branches are waving in the sun.
John Piper, God’s Passion for His Glory: Living the Vision of Jonathan Edwards (Wheaton, IL: Crossway, 1998), 67-68.