Greek and Roman civilization were not western civilization. Western Civilization rose from the ashes of the dark ages and it's rise was largely the result of the injection of Christianity (therefore Judaism) into a then pagan culture.
So I think Praeger's point is fair. The dark ages was a huge civilizational break. While the Greek and Roman influence persists, the emergence from the dark ages coincided with the Christianization of Europe. So Judaeo-Christian values in marriage, amongst other things, were at least coincident with the rise of what we now call Western Civilization and clearly distinguish it from it's predecessors in Greece and Rome.
>>But the part I commenting was about making Western civilization possible.
That’s a different definition of Western civilization than I had in mind and certainly different than taught in the “Origins of Western Civilization” I studied at a conservative Christian school...
but that doesn’t make you wrong. And if the author is using your definition then I can see how he reached his conclusions.