The volume edited by Karine Schomer and W. H. McLeod remains the standard treatment of the sants as a single subject, and one of its useful arguments is that the category is a modern scholarly construction laid over poets who did not think of themselves as members of a movement. There was no order, no initiation and no common institution. What the figures share is a manner of teaching and a set of positions, and later traditions have grouped them in ways that serve those traditions' own purposes.
The most consequential grouping is scriptural. The Guru Granth Sahib, the Sikh scripture, includes compositions by fifteen figures who were not Sikh Gurus, among them Kabir, Ravidas, Namdev, Farid and Dhanna, and the inclusion places verses of a Muslim Sufi and of poets from castes at the bottom of the social order in the same canonical volume as the Gurus. That is a deliberate act with an argument inside it, and it means the sants are read daily in a setting quite different from the one they composed in.
Kabir is the figure who resists the boundaries most stubbornly. Verses attributed to him survive in the Sikh scripture, in the Bijak of the Kabirpanth, and in the Rajasthani collections, and the three versions differ; he is claimed as a Hindu, as a Muslim and as neither, and the legend of his death has Hindus and Muslims disputing his body and finding flowers under the cloth. The story is legend, and it is also an accurate statement of the problem he presents to anyone who wants to file him.