"these sometimes murderous divisions were not the symptoms of a movement without coherent identity, but just the opposite. Controversy arose precisely because 'unlike the religion of the Greeks and the Romans,' Christianity was more than a set of rituals: 'Christians affirmed that certain things were true' (and others, therefore, false). Such a religion 'does not lend itself to every possible opinion; it imposes limits that cannot be formulated in advance, but become evident over time.'
"This evolution and hardening of Christianity's doctrinal core, into what the Victorian Cardinal Manning liked to call the beauty of inflexibility, involved both the acceptance of martyrdom and the proclamation of creeds. But it was also what gave the movement its staying power, and enabled it to prevail over the more yielding polytheism of the society in which it first found itself. Paradoxically, the existence of self-imposed limits on the adaptability of Christian belief was the key to the movement's ability to thrive in dramatically different cultural settings."
Eamon Duffy, reviewing Robert Louis Wilken's The first thousand years: a global history of Christianity (New Haven: Yale University Press, 2012), in "The staying power of Christianity," New York review of books 60, no. 11 (June 20, 2013): 70. Cf. http://liberlocorumcommunium.blogspot.com/2009/07/furst-on-two-contributions-of.html, http://liberlocorumcommunium.blogspot.com/2008/07/frst-on.html.