Survey of Reformed doctors, beginning with Tilenus: natural as opposed to supernatural, as natural as the substantial form
To make the Reformed school's view on this question clearer and surer, it will be worth setting out briefly how some of its leading teachers explain their meaning, all the more because there might seem to be some difference among them here.
Tilenus comes first. In the first part of his Syntagma of Theology, disputation 33, thesis 14, he says that original righteousness is rightly called natural in the sense in which natural and supernatural are set against each other and distinguished. In thesis 17 he says that this quality of original righteousness was as natural to our first parent as nature itself and the substantial form he received in creation. And in the thesis before that he says the quality shone out at once from God's original image in man, as accidents commonly do from their subjects.
Latin
XXVII. Sed ut clarius & certius in hac quaestione Scholae Reformatae sententia percipiatur, operae pretium erit breviter hic referre, quomodo praecipui aliquot illius Doctores mentem suam hac de re explicent: maxime cum videri posset inter eos hic esse nonnulla diversitas. Primum igitur Tilenus Syntagmatis Theologici parte prima, Disputatione trigesima tertia, Thesi decima quarta asserit, justitiam illam recte dici naturalem, eo sensu quo naturalia & supernaturalia mutuo sibi opponuntur, & ab invicem distinguuntur. Thesi vero decima septima dicit tam naturalem primo parenti fuisse hanc justitiae originalis qualitatem, quam erat ipsa natura & forma substantialis per creationem accepta. Adeoque Thesi praecedenti affirmat qualitatem istam ex primigenia Dei in homine imagine confestim emicuisse, ut solent accidentia ex subjectis suis.