Tim Keller wants us to change the culture; he's dissatisfied with the status quo. He wants a revolution of vanguards. It’s always a mistake when Christians are called upon to cry “Revolution.” The cry of Believers should be "Reformation", not revolution. In Scripture, we aren't called to change our culture--we are called to bring Jesus to all of humankind, and the by-product of that is then, a changed culture. Keller tries to sanctify Socialist philosophers such as Gustavo Gutierrez and Karl Marx and call their ideology Scriptural in order to ignite a cultural revolution that is nothing more than godless human endeavors to save a dying world.