Thomas Aquinas

“ Secondly, a thing is incorruptible in its form, inasmuch as being by nature corruptible, yet it has an inherent disposition which preserves it wholly from corruption; and this is called incorruptibility of glory; because as Augustine says (Ep. ad Dioscor.) : "God made man's soul of such a powerful nature, that from its fulness of beatitude, there redounds to the body a fulness of health, with the vigor of incorruption." Thirdly, a thing may be incorruptible on the part of its efficient cause; in this sense man was incorruptible and immortal in the state of innocence. ”

“ For man's body was indissoluble not by reason of any intrinsic vigor of immortality, but by reason of a supernatural force given by God to the soul, whereby it was enabled to preserve the body from all corruption so long as it remained itself subject to God. ”

“ I answer that, The tree of life in a certain degree was the cause of immortality, but not absolutely. To understand this, we must observe that in the primitive state man possessed, for the preservation of life, two remedies, against two defects. One of these defects was the lost of humidity by the action of natural heat, which acts as the soul's instrument: as a remedy against such loss man was provided with food, taken from the other trees of paradise, as now we are provided with the food, which we take for the same purpose. ”