Thomas Aquinas, Compendium of Theology

The blessing of original justice was conferred by God on the human race in the person of its first parent, in such a way that it was to be transmitted to his posterity through him. But when a cause is removed, the effect cannot follow. Therefore, when the first man stripped himself of this good by his sin, all his descendants were likewise deprived of it. And so for all time, that is, ever since the sin of the first parent, all men come into the world bereft of original justice and burdened with the defects that attend its loss.

This is in no way against the order of justice, as though God were punishing the sons for the crime of their first father. For the punishment in question is no more than the withdrawing of goods that were supernaturally granted by God to the first man for transmission, through him, to others. These others had no right to such goods, except so far as the gifts were to be passed on to them through their first parent. In the same way a king may reward a soldier with the grant of an estate, which is to be handed on by him to his heirs. If the soldier then commits a crime against the king, and so is adjudged to forfeit the estate, it cannot afterwards pass to his heirs. In this case the sons are justly dispossessed in consequence of their father's crime.