6th point is just double predestination -- 7th seems a little strange to suggest alongside the other points. Sounds more like a rebuttal than a main point, but Piper's his own man, I guess.
http://www.desiringgod.org/ResourceLibr ... Calvinist/
Piper isn't seeking to add two more points, but is simply calling attention to his belief in the traditional five points (total depravity, unconditional election, limited atonement, irresistible grace, and perseverance of the saints) in a way that also points toward two additional "Calvinistic" truths that follow from them: double predestination and the best-of-all-possible worlds.
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The "seventh" point, the best-of-all-possible worlds, means that God governs the course of history so that, in the long run, His glory will be more fully displayed and His people more fully satisfied than would have been the case in any other world. If we look only at the way things are now in the present era of this fallen world, this is not the best-of-all-possible worlds. But if we look at the whole course of history, from creation to redemption to eternity and beyond, and see the entirety of God's plan, it is the best-of-all-possible plans and leads to the best-of-all-possible eternities. And therefore this universe (and the events that happen in it from creation into eternity, taken as a whole) is the best-of-all-possible-worlds.
