I ran across John Calvin’s tract against the German Interim and discovered a more Medieval explanation of original sin than what he sets forth in his Institutes. I call Calvin’s demonstration in this tract “Medieval” because it mirrors the teaching of Thomas Aquinas, who taught that original sin was a privation of original justice formally and an added habit of concupiscence materially. I have provided the Latin with translations to follow each paragraph.
Deus creavit initio hominem ad imaginem & similitudinem suam, eum que gratia ornavit, & fecit per originalem iustitiam, ut esset omnibut cum corporis, tum animi viribus rectus, nec agitaretur ullis turpidis & pravis motibus: sed in eo caro spiritui, atque inferiores animi vires superioribus, quae tantum ad bonum hortabantur, parerent. (John Calvin, Interim Adultero-Germanum: cui adiecta est vera Christianae pacificationis, et ecclesiae reformandae ratio, p. 3)
God created man in the beginning in his image and likeness and adorned him with grace and by means of original justice made him to be upright in all the powers of the body and the soul, and unable to be shaken by anything foul or by perverse movements: but in him the flesh was obedient to the spirit, and also the inferior powers of the soul were obedient to the superior, which were so strongly encouraging him to good.
Verum, postquam premus parens noster contra, quam mandaverat Deus, fecit: incidit in poenam a Deo propositam, & iustitiae originalis donum pulcherrimum amisit: hinc carentia iustitiae huius, una cum vitioso concupiscentiae habitu, quae spiritui & superioribus animi viribus perpetuo repugnat. Quod peccatu, hoc est, privationem illius iustitiae, qua parte rationem subditam reddebat Deo, una cum concupiscentia in omnem posteritatem suam propagavit… (ibid., p. 4)
But after our first parent acted against God’s commandment he fell into the penalty proposed by God and lost the most beautiful gift (donum pulcherrimum) of original justice; hence there was a loss of justice, together with the vicious habit of concupiscence which continually battles with the spirit and the superior powers of the soul. Which sin, that is the privation of justice, by which it rendered reason subject to God, together with concupiscence, he passed down to all his posterity.