The Sufi tradition contains a vast metaphysical and cosmological set of doctrines elaborated over a long period by masters of gnosis. It contains methods of spiritual realization that address nearly all the different spiritual possibilities on the levels of action, love, and knowledge. It has preserved over many centuries going back to the Prophet a regular chain of transmission of initiatic power (walayah/wilayah) and the grace (al-barakah) necessary for the spiritual journey. And above all, it can enable men and women to reach a state of sanctity.
— Seyyed Hossein Nasr, The Garden of Truth