Thank you for the essay, Dr. Clark, I enjoyed reading it. However, I don't think the following characterization of Redeemer was entirely fair:

"Recently Tim Keller suggested a sort of pluralistic approach to church planting that implies a sort of diffidence to the Reformed theology, piety, and practice than renders them mere preferences rather than matters of principle."

Obviously as a member of Redeemer I'm biased, but to be fair, Redeemer has never "planted" a non-PCA church. They do partner with other churches, and do give financial aid to other Reformed churches, but to say it implies diffidence or that these are simply "preferences" is a bit much. Here's Tim Keller on the subject:

"We do, however, support churches that are Reformed but charismatic (e.g. like C.J. Mahaney’s churches or other similar churches) and other non-Presbyterian churches that we train and we feel are on the same page with us about gospel theology. There are plenty of Baptist, charismatic, churches etc etc that are similar to us in soteriology–are moving toward us. But we put far, far more money into Presbyterian church plants. That keeps us from on the one hand, being sectarian and thinking God only blesses Presbyterian government, but it means on the other hand we give pride of place to our own tradition, which we love. We’ve always identified as ‘Presbyterian’ in our name, as one example."

__________________
Mason
Member, Redeemer Presbyterian Church (PCA)
New York, NY

"Come now, and let us reason together," says the Lord, "Though your sins are like scarlet, they shall be as white as snow; though they are red like crimson, they shall be as wool." - Isaiah 1:18