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.
Holiness is the proper proof of Christianity.
Doctrine alone does not convert. The doctrine plus a saint does. The saint is the doctrine made visible — the embodied argument that the Gospel is not merely true on paper.
Across nineteen centuries, in every culture Christianity has reached, the same kind of human being has been produced: marked by joyful self-gift, peace under suffering, and an enlarged capacity to love unattractive people.
This kind of person is not produced by other ideologies in anything like the same density. The fact is unwelcome but it is a fact.