Charles W. Hedrick Jr.,
History and Silence: Purge and Rehabilitation of Memory in Late Antiquity (Austin: University of Texas Press, 2000), p. 47, with note on p. 268:
Paganism was by its very nature agglutinative, inclusive: there is no
inherent reason why the god of the Christians should not have been worshiped along with Zeus and Mars. From a pagan perspective Christianity
might be regarded as just another oriental cult, like that of Mithra or the
Magna Mater—and many such flourished side by side in late antique Rome.
So the leading characteristic of paganism could be considered its religious
tolerance. Christians, on the other hand, regarded their god as preemptive:
one could not be a Christian and worship other gods. The dichotomy of
pagan versus Christian is a characteristically Christian opposition, as it is the
distinguishing characteristic of Christianity to make exclusionary religious
distinctions.34
34. This argument is made in O'Donnell 1979b.
The reference is to James J. O'Donnell, "The Demise of Paganism,"
Traditio 35 (1979) 45–88. See e.g. O'Donnell, p. 52:
In summary, it is necessary to look upon the religious sociology
of the fourth century with two separate (if often, and confusingly, overlapping)
distinctions in mind: that between worshippers of Christ and worshippers of
other gods; and that between men who could accept a plurality of worships
and those who insisted on the validity of a single form of religious experience
to the exclusion of all others.