In 726, the Emperor Leo III and a group of overzealous "puritans," arguing that misinterpretation of religious images leads to heresy, banned all pictorial representations and began a systematic destruction of holy images, known as the period of iconoclasm (cf. the scene of whitewashing the images from the Khludov Psalter). Referring to the decrees of the Fourth Ecumenical Synod (Council) in Chalcedon (451) which defined that in Christ the two natures, human and divine, are united without confusion and without separation, the iconoclasts rejected the images of Christ because for them they were simply material images which either confused or separated the two natures of Christ. Such confusion or separation, in the iconoclasts' opinion, was tantamount to the heresies of Nestorianism, Arianism or Monophysitism.