In keeping with Sufism's attentiveness to the exoteric and esoteric, to the outer and inner, there is a sense of what is Real and what is Unreal. Because of the fall of Adam, a veil was put in place between humans and God. The whole universe and everything in it, in fact, are a veil. If that veil were gone, humans would be able to perceive that the only truly existing Being was God. The paradox of the veil, simply stated, is that things are not God, but God is nonetheless present in everything. Sufism is aimed at lifting the symbolic veil between the heart of the believer and the True Reality of God.
The symbolism of the veil is bound up in the symbolic nature of the universe itself. Most Sufis agree that the perception of God is not something facilitated by actually seeing with one's eyes, but is a beholding that takes place in one's heart. In the Quran, several references to veils refer to that which stands between the believer and God, a barrier that will be removed for the righteous after the Day of Judgment (83:15). In the hadith literature, Muhammad states of God's veil that "were he to remove it, the glories of His face would burn away everything that eyesight perceives." In another version of this hadith, the veil is made of light, which itself seems paradoxical since that which usually illuminates here refers to something that obscures. According to a 10th-century Sufi treatise, Muhammad used to pray, "Oh God, show us things as they truly are," in reference to the simultaneously outer and inner disposition of the universe. In the 11th century, another Sufi said that the veils of the universe consisted of the world, the self, other people, and Satan.
The word used for the removing of the veil comes from the Arabic word for uncovering, kashf. In the 12th century, Sufi commentator Rashid al-Din Maybudi wrote a treatise entitled The Unveiling of the Mysteries, in which he enumerated seven veils: reason, knowledge, the heart, the self, senses, desire, and will. In general, the veil has been invoked by Sufis throughout the centuries as a symbol of all obstacles on the path to God. The veil represents all Unreality, that is, all that is not God. By removing it, or seeing through and past it, the Sufi apprehends the only True Reality, God Himself.
While certain forms of dress have also become emblematic of Sufism, such as the flowing white robes of the whirling dervishes of Turkey, there is no official "uniform" or dress code for Sufis. It is possible to think of this lack of external markings as another instance of Sufism's emphasis on the inner state, as opposed to a particular outer appearance.