Inayat began to travel and lecture first in the United States and later in Europe. He traveled widely between 1910 and 1920. He decided to do more intensive teaching during the summer in France, and took up residence there near Paris in Suresnes where he could hold his "summer schools".
His teaching strongly emphasized the fundamental oneness of all religions. He was deeply concerned that many of the western religious traditions had lost knowledge of the "science of soul", and the prayer and meditation techniques necessary to develop higher consciousness in mankind.
This Sufi universalism, or interest in and respect for different religions is reflected in a saying by the thirteenth century Andalusian Sufi teacher Ibn 'Arabi. This respected scholar and mystic who authored among other works the classic Sufi retreat manual Journey To The Lord Of Power wrote:
Beware of confining yourself to a particular belief and denying all else, for much good would elude you - indeed, the knowledge of reality would elude you. Be in yourself for all forms of belief, for God is too vast and tremendous to be restricted to one belief rather than another. (Awakening - A Sufi Experience by Pir Vilayat Inayat Khan, Jeremy P. Tarcher - Putnam, New York, 1999, p. VIII), (Original source: Ibn 'Arabi, Fusus al-Hikam, edited by Abu al-'Ala 'Afifi, 2 parts (Beirut: Dar al-Kitab al-'Arabi, 1980), 1: 119))
It was at Suresnes that Inayat developed the Universal Worship service that is now associated with the "Sufi Order in the West". The ritual consists of an invocation, a reading from one of the holy books of the world's major religions, and the lighting of a candle for each tradition. A candle is also lit for all those individuals or religious systems (unknown or forgotten) that have inspired mankind. The ritual continues with a discourse, and ends with a blessing. One goal of the Universal Worship service is to show people from different cultures the many common elements they share in their religious traditions, and to create a sense of unity among people from different cultures by teaching them to read each other's scriptures and "pray each other's prayers".