Wilken on the early Christian redefinition of "religion"

This semester, I’m having one section of NT students read Robert Louis Wilken’s The Christians as the Romans Saw Them, Second Ed. (Yale University Press, 2003).  Wilken traces the views of various Romans (including Pliny, Galen, Celsus, Porphyry, and Julian the Apostate).  Wilken stresses the fact that the Romans were a religious people (contra those who see them as irreligious and thus something of easy pickings for a movement like Christianity) but that their understanding of religion was fundamentally different than that of the early Christians.  One example of this was the Christian view of their religion as distinct from their national or ethnic identity.  Here are some of comments from his discussion of how Celsus viewed the early Christians:

Celsus sensed that Christians had severed the traditional bond between religion and a “nation” or people.  The ancients took for granted that religion was indissolubly linked to a particular city or people. Indeed there was no term for religion in the sense we now use it to refer to beliefs and practices of a specific group or people or of a voluntary association divorced from ethnic or national identity….  The idea of an association of people bound together by a religious allegiance with its own traditions and beliefs, its own history, and its own way of life independent of a particular city or nation was foreign to the ancients.  Religion belonged to a people, and it was bestowed on an individual by the people or nation from which one came or in which one lived… (pp. 124-125).

I am struck at how Christianity not only introduced a religion that transcended culture but that it was based on personal, individual beliefs and practices.  It teaches the necessity of conversion, repentance, and faith.  For those in the Western world, influenced by the success of the Christian movement, we take it for granted that this is the way religion works.  This was not, however, the way pre-Christian, pagan Romans viewed religion, and this is likely not the way people in cultures not influenced by Christianity see it.