Even though Shenxiu and the so-called “Northern School” were subsequently attacked as teaching a gradualist approach to enlightenment, the "Guanxin Lun" (觀心論) ("Treatise on the Contemplation of the Mind"), a Northern text which Zen scholar John McRae claims is “unquestionably written by him ” emphatically states: “It does not take long to witness this (i.e., to realize sagehood); enlightenment is in the instant. Why worry about your white hair (i.e., about your age)?” Shenxiu's exhortations to constant, unremitting practice gave Shenhui the opening to attack the teaching as “gradualist” (a charge which would ironically apply to the entire Dongshan tradition of the Fourth and Fifth Patriarchs). In any case, the vilification of Shenxiu by Shenhui occurred some thirty years after Shenxiu's death. During his lifetime, and especially his relatively brief teaching in the capital cities of the Tang Dynasty, Shenxiu's teachings were received with widespread acceptance and reverence. The influence of Shenxiu's teachings on subsequent Chan doctrine and practices is still a somewhat open question.