THIS excellent edition of Bacon's commentary on the “Liber de Causis” brings nearer to completion the publication of the works of the erudite Franciscan friar of the Middle Ages. The thesis and the commentary are printed separately, following the method used by medieval writers. The history of the MSS. used for this edition is given by Mr. Steele in a comprehensive introduction. The work deals with some fundamental points of ontology, such as being, substance, cause and the intellect. Opera hactenus inedita Rogeri Baconi Fasc. 12: Questiones supra librum de Causis. Nune primum edidit Robert Steele, collaborante Ferdinand M. Delorme. Accedit Liber de Causis a Roberto Steele. Pp, xxiv + 196. (Oxford: Clarendon Press; London: Oxford University Press, 1935.) 17s. 6d. net.