At the moment, I am reading Gerald Bonner's little book called 'Freedom and Necessity' which concerns an outline (or at least the professor's interpretation) of St. Augustine's doctrine on human freedom, grace and predestination.
He quotes from the saint and states that this doctrine is horrifying although essentially the same as one passage of St Paul:
'Two little children are born. If you ask what is due, they both cleave to the lump of perdition. But why does its mother carry the one to grace, while the other is suffocated by its mother in her sleep? Will you tell me what that one deserved which was borne to grace, and what that one deserved whom its sleeping mother suffocated? Both have deserved nothing of good but the potter hath power over the clay, of the same lump to make one vessel unto honour, and another into dishonour...' (Sermon 26)
Such thinking is certainly considered terrifying today, but we must not allow our preconceived notions of love and justice to cloud our apprehension of the truth.
The Doctor of Grace admitted, a child that dies without undergoing the laver of regeneration can not therefore experience the beatific vision, but may receive the mildest of punishments. God certainly allowed one to die and one to live, which is due to His inscrutable wisdom and this is done for His greater glory. If we have to conjecture about such topics let us answer thus:
If that child who was tragically suffocated by it's mother were to be born, it may grow up to commit grave iniquity and accordingly suffer greater torment in Hell. Now, as God orders all creation to His preordained plan in His unsurpassed knowledge, He may allow this to happen to preserve the child from acting in that manner. A state of the mildest punishments is better than not to exist at all.
This logic may be considered draconian or hideous, yet its an attempt (however feeble) to defend God's justice and love.
Also, the saint believed that in some mysterious manner, according to the unity of the human race, all men were present in Adam's loins and therefore guilty of his sin which is transmitted to them.