The textual sources for the Parson's Tale may be usefully differentiated in three classes: the illustrative sources for biblical, patristic, and classical quotations used with or without attribution throughout the treatise, derived either directly from the source texts or indirectly through intermediaries in the following two classes: the contextual sources which provided the initial penitential, aretological, and hamartiological contexts represented in Chaucer's work; and the verbal sources of a more immediate nature which approximate, as nearly as can now be reconstructed, the material which Chaucer drew on more directly for his own presentation of penitential and moral-theological concepts and the verbal formulations in which the reader finds them in the Parson's Tale. The illustrative sources of the Parson's Tale are diverse, but as in many medieval works of moral and pastoral intent, and as is indicated by the texts which Chaucer drew on more directly and which are indexed below (see pp. 612–13), the Parson's Tale is above all indebted to the inspiration of the Vulgate Bible for many of its ideas in direct quotations and paraphrased statements. A wide range of patristic thought is represented in the treatise, as well, in particular that of Augustine of Hippo, Jerome, Gregory the Great, Isidore of Seville, the Glossa ordinaria on the Vulgate bible, Gratian's Decretum, and Bernard of Clairvaux. Classical sources are far less apparent in the Parson's Tale, though Seneca, in particular, has a place here, as he does in many later-medieval treatises on moral theology, and the much more indirect influence of Aristotle stands out, as well. The history of scholarship on the sources of the tale reveals an increasing precision in the identification of the illustrative sources for particular quotations and the intellectual traditions which they represent. In the treatment of the sins, for example, the Parson quotes “the Philosophre” in defining wrath as “the fervent blood of man yquyked in his herte” (ParT X,536). Robert C. Fox first identified the ultimate source of this definition as Seneca's De ira, but as A. V. C. Schmidt then demonstrated, the definition is derived from Aristotle's De anima, which influenced Seneca's formulation. Finally, as Siegfried Wenzel established, the quotation is found with the same attribution to the “Philosophus” in a text which represents one of Chaucer's more direct sources for material on the vices.