Narrating from Imam al-Rida (AS) when a man believing in dualism asked him, 'I believe that the creator of the world are two, so what is the proof that he is One?' The Imam replied, 'Your belief that there are two is proof in itself that he is One, for verily you have only claimed the second after having affirmed the existence of the One. So, the One is already agreed upon -it is more than one that is controversial [and remains to be proven].'