I saw this quote at
What’s the Difference? A Comparison of the Faiths Men Live By by Louis Cassels
and while the quote is attributed to Horden, I don't recall actually reading it myself in the book. :-)

The heart of this movement lies in loyalty to the faith of historic orthodoxy, not because it is ancient or orthodox, but because it is believed to be true. Modern Orthodoxy believes that in the orthodox Christian tradition we have a precious heritage of truth which must not be thrown overboard just because someone has split the atom and someone else has looked farther through a telescope. Nevertheless, it is willing to understand the old truth more fully insofar as modern thought makes that possible."

I like his description of modern orthodoxy. I don't know if it's an accurate description of modern orthodoxy, I just know that it feels comfortable.