The Reformed agree: unfallen man could not-die, but only the risen blessed cannot die
As for the teachers of the Reformed school, they too hold by common consent that man in the state of innocence was immortal in some measure, and they explain that immortality in much the same way.
Like the teachers of the Roman Church, they distinguish the immortality by which someone is unable to die from the immortality by which someone is able not to die and is free from the necessity of dying. In the first sense, they teach, only the blessed after the resurrection will be immortal. Man in his unfallen state was immortal only in the second sense: he had the possibility of dying, which the blessed do not have, but not the necessity of dying, which we now have through sin.
Latin
XIX. Quod spectat autem Scholae Reformatae Doctores, illi quoque communi consensu docent hominem in statu innocentiae fuisse aliquatenus immortalem. Nec etiam dissimili ratione explicant istam immortalitatem. Nam cum Doctoribus Ecclesiae Romanae, distinguunt inter immortalitatem qua aliquis non potest mori, & inter eam qua aliquis potest non mori, & est a necessitate moriendi immunis. Priori modo solos beatos post resurrectionem immortales fore docent; sed posteriori tantum hominem in statu integro fuisse immortalem; ita ut in eo esset possibilitas moriendi, quae non est in beatis, non esset vero, quae jam est in nobis per peccatum, moriendi necessitas.