Paperback, 510 pages
The book follows the Sufi principle of 'scatter' in answering this unanswerable question. It deliberately shies away from offering an ordered definition. Instead, it throws out ideas.
Like fragments of light on dust particles, they reveal the shape of something intangible. Neither emotionalist nor academic, this book offers the closest thing a written work can to an experience of Sufism.
When it came out in 1964 it was incredibly influential, attracting admirers such as Robert Graves (who wrote the introduction), Ted Hughes and Doris Lessing.