What is the concept of ascetic Sufism, is Al-Hasan Al-Basri attributed to the Sufis, and what is the difference between ascetic Sufism and philosophical Sufism?

The term "Sufism" was not known during the time of the Prophet, peace and blessings be upon him, nor his companions, nor was it widespread during the first three centuries. Attributing it to Hasan al-Basri with its later, specialized meaning is incorrect, as Sufism in this sense had not yet emerged in his time.

Sufism of asceticism refers to the focus on ethics, asceticism, and spiritual refinements, and it is part of the religion of Islam and is encouraged.

As for philosophical Sufism, it is a development that occurred when the path of Sufism deviated from the Salafi methodology, through the introduction of innovative devotional practices and the incorporation of academic issues that arose from the interaction of the scholarly movement with Greek and pagan philosophies, as well as esoteric and Gnostic doctrines.

Sufism began as an individual movement calling for asceticism and intense worship. It then developed into known orders. Sufis aim to purify the soul and elevate it to know Allah through unveiling (kashf) and witnessing (mushahadah), rather than through legitimate Sharia means, which led to its intertwining with pagan philosophies. This philosophical Sufism varies in its distance from the Sunnah, and some of its factions may even commit acts that invalidate one's religion.

The great early Sufi shaykhs followed the doctrine of the Ahl al-Sunnah wa al-Jama'ah (People of the Sunnah and the Community) and the Ahl al-Hadith (People of Hadith). However, some of the later ones followed the methodology of the Ahl al-Kalam (scholastic theologians) in the branches of creed. Philosophical inclination appeared among the later Sufis, and they became divided into three categories: Sufis of Ahl al-Hadith (who are the best of them), Sufis of Ahl al-Kalam (below them), and philosophical Sufis (the atheists).