The "Gnostikos" is the second volume of a trilogy containing the "Praktikos", intended for young monks to achieve "apatheia", i.e. " a state of calm which is the prerequisite for love and knowledge ", in order to purify their intellect and make it impassible to reveal the truth hidden in every being. The third book, "Kephalaia Gnostika", was meant for meditation by advanced monks. Those writings made him one of the most recognized ascetic teachers and scriptural interpreters of his time, which include Clement of Alexandria and Origen. The ascetic literature of early Christianity was influenced by pre-Christian Greek philosophical traditions, especially Plato and Aristotle, looking for the perfect spiritual way of life. According to Clement of Alexandria, Philosophy and Scriptures can be seen as "double expressions of one pattern of knowledge ". According to Evagrius, " body and the soul are there to help the intellect and not to hinder it ". The Arabic word for asceticism is zuhd (Zuhd in Islam). The prophet Muhammad and his followers practiced asceticism. However, contemporary mainstream Islam has not had a tradition of asceticism, but its Sufi groups  – have cherished an ascetic tradition for many centuries. Monasticism is forbidden in Islam. Scholars in the field of Sufi studies have argued that asceticism ("zuhd") served as a precursor to the later doctrinal formations of Sufis that began to emerge in the 10th century through the works of individuals such as al-Junayd, al-Qushayrī, al-Sarrāj, al-Hujwīrī, and others. Sufism grew as a mystical, somewhat hidden tradition in the mainstream Sunni and Shia Islam, state Eric Hanson and Karen Armstrong, likely in reaction to "the growing worldliness of Ummayyad and 'Abassid societies". Acceptance of asceticism emerged in Sufism slowly because it was contrary to the sunnah, states Nile Green, and early Sufis condemned "ascetic practices as unnecessary public displays of what amounted to false piety". The ascetic Sufis were hunted and persecuted by Sunni and Shia rulers, in various centuries. Sufism was adopted and then grew particularly in the frontier areas of Islamic states, where the asceticism of its "fakirs" (or dervish) appealed to a population used to the monastic traditions of Buddhism, Hinduism or Christianity.