The following is a list of the rasa'il (epistles) which compose the influential Neoplatonic encyclopedia, the Encyclopedia of the Brethren of Purity composed by the Brethren of Purity in the tenth century CE in Basra, Iraq. The following tabulation of the rasa'il is principally drawn from a work entitled "Notices of some copies of the Arabic work intitled "Rasàyil Ikhwàm al-cafâ"", written by Aloys Sprenger, originally published by the Journal of the Asiatic Society of Bengal (in Calcutta) in 1848. Doubts have been raised by A. L. Tibawi as to the accuracy of Sprenger's catalogue: "But it is unfortunate that his account is marred by loose translation and too many misreadings of or misprints in the Arabic, and his collection omits the fourteenth tract, merges the eighth with the ninth, and leaves the text of the twelfth and thirteenth confused." Mathematical Sciences Numbers, arithmetic, and numerology, especially Pythagorean; a discussion of the importance of the number four Geometry (jumatriya). Euclid's definitions and how to calculate the area of a triangle Ptolemaic astronomy (asturunumiya) Geography (al-jughrafiya), especially geography that uses mathematics. The Brethren explain racial characteristics as resulting from varying climates' long-term influence. The Brethren seem to know of Japan: "The most eastern country of this climate is the island of Niphon [compare another term for Japan, "Nippon"]; then comes southern China, then the south of Ceylon, then central India, then subcentral and Sindh, then beyond the Persian Gulf the south of Oman then comes the centre of the country of Shir, then central Yaman, then across the Red Sea, central Messynia ; then across the Nile is Nubia....." Music (al-musiqa) deals with the subject in unusually many aspects. It first lays out the power of music and its uses; it uses the practical purposes of music as a defense against various Koranic proscription; another defense is that the restrictions are applicable only to entertainment and pleasure motivated music, analogous to contemporary defenses of poetry). Theologically motivated, it moves on to the abstracted essence of music, which is present in all arts. Deals with ratios and proportions, which are useful in mathematics and also especially in musical scales; indeed, Thomas Davidson describes there assertion thus: "The faculty of aesthetic judgement investigates these properties, and so discovers the rules of Art." Eric van Reijn classifies this epistle as dealing with "Mathematics and Geometry". The seventh and eighth epistles are the "Classification of