Ernest Renan suggested in 1882 that, under different circumstances, Mithraism might have risen to the prominence of modern-day Christianity. Renan wrote: "If the growth of Christianity had been arrested by some mortal malady, the world would have been Mithraic". However, this theory has since been contested. Leonard Boyle wrote in 1987 that "too much ... has been made of the 'threat' of Mithraism to Christianity", pointing out that there are only fifty known mithraea in the entire city of Rome. J. Alvar Ezquerra holds that since the two religions did not share similar aims; there was never any real threat of Mithraism taking over the Roman world. Mithraism had backing from the Roman aristocracy during a time when their conservative values were seen as under attack during the rising tides of Christianity.