The Encyclopedia of the Brethren of Purity (, Rasā'il Ikhwān al-ṣafā') also variously known as the Epistles of the Brethren of Sincerity, Epistles of the Brethren of Purity and Epistles of the Brethren of Purity and Loyal Friends is an Islamic encyclopedia"The work only professes to be an epitome, an outline; its authors lay claim to no originality, they only summarize what others have thought and discovered. What they do lay claim to is system and completeness. The work does profess to contain a systematized, harmonious and co-ordinated view of the universe and life, its origin and destiny, formed out of many discordant, incoherent views; and it does claim to be a 'complete account of all things' - to contain, in epitome, all that was known at the time it was written.
