Excerpted from "Why I am a Muslim" with permission of ThorsonsElement, an imprint of HarperCollins Publishers UK.

When I was 19 years old, I was a first year student at Wellesley College. I lived in a dormitory neighboring our campus lake that shimmered even on the coldest New England winter days. The tradition was that if your beau accompanied you on a walk around the lake three times he must then ask you to marry him.
If he didn't, you were free, even under Wellesley etiquette, to push him into the lake. In nearby Green Hall, I would attend my first college class (of many) on Islam. The woman who would later become my advisor was lecturing us on Islamic mysticism.

The Sufis, she told us, were Muslim mystics--poets, musicians, artists, writers and others-who had a deep love for God. They first emerged in the mid-eighth century in response to the then-Muslim leadership's focus on political affairs. The Sufis wanted to remember Muhammad's emphasis on unity and brotherhood with members of other religions. The Sufis also longed to be with God, and they felt that no one really understood them the way God did. The artistically inclined ones would work themselves up into ecstatic raptures-through dance or poetry.

The famous thirteenth-century Sufi poet Rumi once compared himself to a reed growing by a lake that was ripped from the ground to be used as a reed-flute. Beautiful sounds came out of the reed, which resonated with each listener, capturing their own personal feelings. But the reed wanted to be back in the earth, near the lake. "Like the reed," my teacher told us, "Rumi wanted to be returned to God. His love for God was that strong."

Hearing that poem for the first time, I both understood it and didn't. When I left class that day, I felt as if I were seeing everything for the first time. I saw the fingerprints of God everywhere--in every tree leaf, in the blades of grass and even in the glow of the lake. Some Sufis say that they are actually in love with God and that only God knows them intimately. Once you realize, as Sufis do, that God is in everything, you can't help but always look for Him.

Sufism is the mystical attitude or phenomenon within Islam. It is probably the aspect of Islam that is most attractive to non-Muslims because, generally, Sufism espouses a philosophy of listening to one's heart and emotions to feel the presence of God, rather than, for instance, focusing on strict rules. While all mystical traditions are experiencing a renaissance these days, like the Kabbalah movement of Judaism and the tradition of Catholic mysticism, Sufism has been a catalyst in the Islamic world since it arrived on the scene. Its message is clear and spare, minimalist almost: focus on God.

Every time I am confronted by Sufism's clarity--whether through a Rumi poem or a Sufi folk song--I am stunned by it and seduced by its simplicity and single-minded focus on the one God. Sufism is not a specific sect or branch of Islam but actually cuts through all the various schools and sects. As a result, one can be a Sunni Muslim and also Sufi or an African-American Muslim who holds Sufi ideals and so on. One of my reviewers for this book, Dr. Maher Hathout, who is a scholar of the Qur'an, remarked after reading this chapter, "As a matter of fact, there is a Sufi inside every believing Muslim." Furthermore, while the essence of Sufism is the same from Sufi to Sufi, individual Sufi orders maintain different practices and traditions for worship, passed down for hundreds of years.

The converts to Islam I meet these days either converted because of the lyrics of avowed Muslim rappers like Mos Def or Q-Tip or because of Sufism. They'll tell me how they found a book of poetry by Rumi or Hafiz (another famous Sufi poet, who lived about one hundred years after Rumi) and became immediately hooked. In fact, since the beginning of the Sufi movement, Sufism has assisted the spread of Islam.

Contrary to widespread popular belief, Islam was not really spread by the sword--most Muslim leaders including Muhammad abhorred forced conversion. The Qur'an itself says, "Let there be no compulsion in religion," (2:256) and in my experience, Muslims do not engage in missionary activity. (Judaism has a similar prohibition on missionary activities) However, one could say that Islam was spread by Sufism--not in all areas of the Islamic world, but certainly in South and Central Asia. Muslim conquerors might have gained power in a certain area, but the appeal of the emotion-guided Sufis actually caused the locals to convert or to become more devout Muslims. Even near-illiterate Pakistani rickshaw drivers can sing a Rumi poem to you while they transport you in their colorful conveyance. In South Asia, it is not even uncommon to find a Hindu or Christian praying at the shrine of a Sufi saint; the appeal of Sufism is so strong that it stretched beyond formal religious boundaries years ago.