SINDERESI. – A medieval term equivalent to the modern “moral sense,” understood as “the spiritual quality by which we know the first principles of the practical order, which regulate all practical knowledge” (Y. Simon, Critique de la connaissance morale, Paris 1934, p. 56). S. is therefore distinct, although it is its ultimate root, from “moral conscience” (συνείδησις).
The term seems to derive from συνενηρέα, I look attentively, I observe, and was used by the Stoics; but it is doubtful whether they saw a difference in meaning between συνενηρέσεις and συνείδησις (cf. M. Waldmann, Synteresis oder Synedesis? Ein Beitrag zur Lehre vom Gewissen, in Theol. Quartalschr., 109 [1938], pp. 323 ff.). It entered scholasticism through a text of s. Girolamo, who, above the three faculties of the soul (rational, irascible, concupiscible), places a fourth “quam Graeci vocant συνενηρεσιν, quae scintilla conscientiæ in Cain quoque pectore, postquam eiectus est de paradiso, non extinguitur, et qua victi voluptatibus vel furore, ipsaque interdum rationis decepti similitudine, nos peccare sentimus... Et tamen hanc quoque conscientiam... cernimus praecipitari apud quosdam et suum locum ammittere...” (Comm. in Ezech., I, cap. 1: PL 25, 22). Among the scholastics, the term is already found in Magister Udo, in his commentary (ca. 1160) on Pietro Lombardo, who was the first to examine the text of s. Girolamo (Libri IV sententiarum, II, dist. 39, at the end). Studied and interpreted in various ways in the 12th and 13th centuries, s. received its two fundamental interpretations from s. Bonaventura and s. Tommaso. S. Bonaventura (In II Sent., dist. 39, aa. 1-2) considers s. as “potentiam effectivam inquantum naturaliter habilis est ad bonum et ad bonum tendit,” that is, the natural will itself, insofar as it is inclined toward moral good; it is therefore distinct from conscience, which is “naturale iudiciatorium, dirigens ipsum intellectum in conoscendis.” S. Tommaso, on the other hand (In II Sent., dist. 24, q. 2, aa. 3-4; dist. 39, q. 3, a. 1; De verit., q. 16; Sum. Theol., 1ª, q. 79, aa. 12-13; 1ª-2ª, q. 94, a. 1; 2ª-2ª, q. 47, a. 6), places s. on the plane of practical knowledge, as a natural intellectual habit of the first principles directing human activity.