The transformation of saints is empirical
The claim
Christianity has produced, in every generation, a recognizable kind of person — Francis, Teresa of Avila, Vincent de Paul, Maximilian Kolbe, Mother Teresa — whose lives are difficult to explain on naturalist grounds.
These are not pious legends. They are people whose biographies are documented, whose holiness was tested under extreme pressure, and whose effect on those around them was transformative. A tree is known by its fruit. Strange fruit, repeated for two thousand years, is data.
The covenant family produces these lives by structural reason.
Christianity is not primarily an ethics or a philosophy. It is a covenant — God's binding self-gift to a family he is gathering. Inside that family, the ordinary means of grace (Eucharist, confession, Scripture, prayer) reshape persons over time.
The saints are not super-Christians. They are the ordinary outcome of the ordinary means, when the means are not resisted.
What needs explaining is not that there are saints. It is that there are not more.