Found in The Great Heresies by Hilaire Belloc: He [Mohammed] refused to know anything of the Eucharist, with its Real Presence; he stopped the sacrifice of the Mass, and therefore the institution of a special priesthood. In other words, he, like so many lesser heresiarchs, founded his heresy on simplification. Catholic doctrine was true (he seemed to say), but it had become encumbered with false accretions; it had become complicated by needless man-made additions, including the idea that its founder was Divine, and the growth of a parasitical caste of priests who battened on a late, imagined, system of Sacraments which they alone could administer. All those corrupt accretions must be swept away. There is thus a very great deal in common between the enthusiasm with which Mohammed's teaching attacked the priesthood, the Mass and the Sacraments, and the enthusiasm with which Calvinism, the central motive force of the Reformation, did the same. I can't help but wonder why the Reformation was right but Mohammed was wrong?