The BPS also publishes several books on the Abhidhamma, a systematic arrangement of the Buddha's philosophical and psychological teachings, defining the theory that lies behind his more pragmatically oriented discourses: "A Comprehensive Manual of Abhidhamma", a translation of the "Abhidhammattha-sangaha" complete with a detailed explanatory guide by the Burmese Sayadaw U Rewatadhamma and Bhikkhu Bodhi. Nyanaponika Thera's "Abhidhamma Studies" demonstrates the practical relevance of the Abhidhamma to the spiritual life. To find one's way through the seven books of the canonical Abhidhamma, Nyanatiloka Thera's "Guide through the Abhidhamma Pitaka" is of great use. For exploring the full range of classical Theravada thought Achariya Buddhaghosa's masterpiece, The "Visuddhimagga" is essential. This is a virtual encyclopaedia of Buddhist doctrine and meditation, which gives detailed coverage to all the meditation subjects and, in its middle chapters, a survey of the Abhidhamma. This is published by BPS in the outstanding translation by Bhikkhu Ñanamoli under the title "The Path of Purification." The BPS also publishes the translation of an earlier, shorter work, the "Vimuttimagga" or "Path of Freedom," which served as the example for the "Visuddhimagga," and which is only completely extant in a Chinese translation. A draft translation from the Chinese was done by N.R.M. Ehara, Soma Thera and Kheminda Thera. A new translation of this important work is currently being done by Bhikkhu Nyanatusita.