Nicene and Post-Nicene Fathers, Vol. V:
A Treatise on Rebuke and Grace.: Chapter 33

Chapter 33 [XII.]—What is the Difference Between the Ability Not to Sin, to Die, and Forsake Good, and the Inability to Sin, to Die, and to Forsake Good?

On which account we must consider with diligence and attention in what respect those pairs differ from one another,—to be able not to sin, and not to be able to sin; to be able not to die, and not to be able to die; to be able not to forsake good, and not to be able to forsake good. For the first man was able not to sin, was able not to die, was able not to forsake good. Are we to say that he who had such a free will could not sin? Or that he to whom it was said, “If thou shalt sin thou shalt die by death,” could not die? Or that he could not forsake good, when he would forsake this by sinning, and so die? Therefore the first liberty of the will was to be able not to sin, the last will be much greater, not to be able to sin; the first immortality was to be able not to die, the last will be much greater, not to be able to die; the first was the power of perseverance, to be able not to forsake good—the last will be the felicity of perseverance, not to be able to forsake good. But because the last blessings will be preferable and better, were those first ones, therefore, either no blessings at all, or trifling ones?