Sufism is the esoteric aspect of Islam. In modern language it might also be referred to as "Islamic spirituality". It is that mode of the religious life of the Sufi in Islamin which the emphasis is placed not so much on the performances of external ritual as on the activities of the inner life. Two origins of the word sufi have been suggested. Commonly, the lexical root of the word is traced to ṣafā, which in Arabic means "purity". Another origin is ṣūf, "wool", referring to the simple cloaks the early Muslim ascetics wore. According to the medieval Iranian scholar Abu Ryhan al-Biruni, the word sūfi is derived from the Greek word sofia sofia (σοφία), meaning wisdom.

I define the world sufi in wide terms by applying it to anyone who believes that it is possible to gave direct experience of God and who is prepared to go out of his way to put himself in a state whereby he may be enabled to do this. – J. Spencer Trimingham.

Although philosophies vary between different Sufi sects, Sufism as a whole is primarily concerned with direct personal experience, and as such is often compared to Zen Buddhism and Gnosticism. Gnosticism is a blanket term for various religions and sects most prominent in the first few centuries A.D. Many elements of Neoplatonism and Gnosticism are pre-Christian, and it is generally accepted that orthodox Christianity and its canonical text. The Greek mystical ideas were in the air and easily accessible to the Moslem inhabitants of Western Asia and Egypt, where the Sufi theosophy first took shape. When it is added that much of speculation of Sufism agrees with that we find, for example, in the writings of Dionysius the Areopagite , we are drawn irresistibly to the conclusion that Neoplatonism poured into Islam a large tincture of the same mystical element in which Christianity already steeped.

Sufism is a particular method of approach to the Reality (haqiqa), making use of intuitive and emotional spiritual faculties which are generally dormant and latent unless called into play through training under guidance. Hence the great importance the guides attached to permission to recite mystical exercises and undertake retreats for thereby the burden is adjusted to the capacity of the individual. An tariqa was a practical method to guide a seeker by tracing a way of thought, feeling and action, leading through a succession of stages in integral association with psychological experiences called “states” to experience of divine Reality At first tariqa meant this gradual method of contemplative mysticism.

Circles of disciples began to gather around an acknowledged master of the Way, seeking training through association or companionship. The names of certain of these early masters were incorporated in the mystical lineage of the tariqas. Many Sufi practitioners are organized into a very diverse range of brotherhoods. Although many orders ("tariqas") can be classified as Shi’a or Sunni or even both, there are a few that are clearly not either Shiah or Sunni and so constitute a separate sphere of Islamic faith. Sufis believe that their teachings are the essence of every religion, and indeed of the evolution of humanity as a whole. The central concept in Sufism is " love". Dervishes - the name given to initiates of sufi orders - believe that love is a projection of the essence of God to the universe.

The Sufi who sets out to seek God calls himself a traveller (salik). He advances by slow stages along a path (tariqat) to the goal o union with Reality. – Reynold Nicholson.

Classical Sufis were characterised by their attachment to dhikr (or zikr) and ascetism. Dhikr is the remembrance of God through a specific devotional act, such as the repetition of divine names, supplications and aphorisms from Hadith literature and the Qur'an. More generally, dhikr takes a wide range and various layers of meaning. This includes dhikr as any activity in which the Muslim maintains awareness of God. To engage in dhikr is to practice consciousness of the Divine Presence and love. Ibn al-Arabi declares that no religion is more sublime than a religion of love and longing for God. Love is the essence of all creeds the true mystic welcomes it whatever gusie it may assume. «Love» says Jalaluddin «is the remedy of our pride and self-conceit, the physician of all our infirmities».

To have been divested of all “otherness” is to have attained the degree of Universal Man, who is also called the Sufi. But strictly speaking it cannot be considered as a degree at all. It is no less than the Eternal and Infinite Oneness of God, the Certainty of Whose Truth burns up all except Itself. Therefore it is sometimes said that “Sufi is not created”, since the Truth Itself in not created and It has burnt up in the Sufi all that was created, leaving only Itself. - Abu Bakr Siraj Ed-Din

Thus, Sufism has been characterized as the science of the states of the lower self (the ego), and the way of purifying this self of its reprehensible traits, while adorning it instead with what is praiseworthy, whether or not this process of cleansing and purifying the heart is in time rewarded by esoteric knowledge of God. This can be conceived in terms of two basic types of law, an outer law concerned with actions, and an inner law concerned with the human heart. The outer law consists of rules pertaining to worship, transactions, marriage, judicial rulings. The inner law of Sufism consists of rules about repentance from sin, the purging of contemptible qualities and evil traits of character, and adornment with virtues and good character.

Neo-Sufism and "Universal Sufism" are terms used to denote forms of Sufism that do not require adherence to Shariah, or a Muslim faith. The terms are not always accepted by those it is applied to. The Universal Sufism movement was founded by Hazrat Inayat Khan, teaches the essential unity of all faiths, and accepts members of all creeds. Sufism Reoriented is an offshoot of Khan's Western Sufism influenced by the syncretistic teacher Meher Baba.