 Fârâbî’s most widely-known and perhaps best-understood work, the Principles of the Opinions of the People of the Perfect City, and his often similar Political Regime, presuppose analyses of being and unity in arguing for conclusions about God and his attributes and his causality; but Fârâbî makes these analyses fully explicit only in two much less widely known and less well-understood texts, the Kitâb al-ḥurûf = Book of Letters and On the One and Unity, which are intended to be read together. Both of these texts were edited for the first time by Muhsin Mahdi, the Book of Letters in 1969 and On the One and Unity in 1989; only partial translations of the Book of Letters, and no translations at all of On the One and Unity, have been published in English or any western European  language.[14]  Both texts are difficult, and at least the Book of Letters presents serious textual problems; there have been few studies of On the One and Unity, and most studies of the Book of Letters have focussed on its socio-political rather than metaphysical  sections.[15]  So what is said here must remain tentative.