Christian polemicists privileged Muhammad’s self-denial of miracles as their key evidence

Evidence

Peter may have had no clear picture of the relations of Muhammad to the Quraysh in Mecca; but he certainly knew that Moses, and still more Christ and the Apostles, had encountered unbelief. It seemed important to him, as to so many, that Muhammad had himself denied that he had this power; this was treated as though it were a confession on Muhammad’s part that he was not what he pretended. — Norman Daniel, Islam and the West, 425