For when they hear from us the following: if what is mortal is to pass into life, then, since the first birth leads into mortal life, another birth had to be found. This second birth neither begins from corruption nor ends in corruption, but leads the one born through it into immortal life. Thus, just as what is born from mortal birth necessarily comes to be mortal, what is born from a birth that does not admit corruption may become stronger than the corruption that comes from death. Yet when they hear these and similar things, and are also taught the manner in which the mystery of regeneration is fulfilled—through prayer to God, invocation of heavenly grace, water, and faith—they remain hard to persuade. They look at what is visible, as though the bodily action did not correspond to the promise.
For they say, 'How can prayer and the invocation of divine power over the water become a source of life for those who have been initiated?' Unless they are excessively obstinate, a simple argument is enough to bring them to assent to the teaching. Let us ask them in return, since the manner of bodily generation is evident to everyone: how does what is deposited as the beginning of the formation of a living being become a human being? In that case there is no argument that can discover by reasoning even a probable explanation.
For what does the definition of a human being have in common with the quality observed in that material? A human being is rational and capable of thought, receptive of understanding and knowledge; but that material is observed simply as having a certain moist quality, and thought grasps nothing in it beyond what is perceived by the senses. Therefore the answer we would expect from those whom we asked how it is credible that a human being is constituted from that material is the same answer we give when we are asked about regeneration through water.
For in that case anyone who is asked can readily answer that the material becomes a human being by divine power; without that power it remains motionless and inactive. If, then, it is not the underlying material that makes the human being, but divine power that transforms what is visible into human nature, it would be extreme inconsistency to acknowledge such power in God there and yet suppose that, in this case, the divine is too weak to fulfill His will.
'What does water have in common with life?' they ask. We will ask them in return, 'What does moisture have in common with the image of God?' Yet there is nothing strange in the first case if, when God wills it, what is moist passes into the most honored living being. In the same way, we say there is nothing astonishing here if the presence of divine power transforms what has come to be in a corruptible nature toward incorruption.