VATICAN CITY (CNS) — Purgatory is like a purifying fire burning inside a person, a painful experience of regret for one’s sins, Pope Benedict XVI said.

“A soul stained by sin cannot present itself to God,” the Pope said Jan. 12 at his weekly general audience.

The Pope spoke about purgatory in an audience talk dedicated to the life and mystical writings of St. Catherine of Genoa, a 15th-century married woman who ran Genoa’s largest hospital.

Married at age 16 to an older man with a gambling problem, she initially lived a very worldly life, the Pope said, but after about 10 years, she was struck by the emptiness of her life, especially in comparison to the greatness of God’s love.

She began a “life of purification, which, for a long time, made her experience constant pain for the sins she committed and pushed her to impose penances and sacrifices on herself to demonstrate her love to God,” the Pope said.

Although she is the author of a Treatise on Purgatory, Pope Benedict said, “she never received specific revelations about purgatory or the souls that are being purified there.”

Rather, her deep prayer and focus on the conflict between human sin and God’s love led her to understand how logically a person who has sinned would not be worthy to be in the presence of an all-loving, all-perfect God, the Pope said.

Unlike most Catholics of her day, he said, she was convinced purgatory was not a place, but a process.

Suffering is purgatory, the Pope said. “The soul that is aware of the immense love and perfect justice of God consequently suffers for not having responded correctly and perfectly to that love.”