This chapter discusses the important developments in the philosophy of the soul that took place between around 1150 and 1215, which played a role in early Franciscan thought on human nature. These include the introduction of medical sources translated from Greek and Arabic into Latin, and, above all, the translation of Greek and Arabic philosophical works in the latter half of the twelfth century. The chapter explores the factors which mitigated the reception of those sources in the early thirteenth century and the reasons why their appropriation is particularly extensive in the work of John of La Rochelle.