As the model for the saint, Caravaggio controversially chose Fillide Melandroni, a well known Roman prostitute he had fallen in love with and who caused him many problems.

Fillide would again model for him in Martha and Mary Magdalene, Judith Beheading Holofernes, and in a single portrait burned in Berlin during World War II.

At the age of 18, she confronted the Roman Emperor Maximus (presumably this refers to Galerius Maximianus), debated his pagan philosophers, and succeeded in converting many of them to Christianity.

Maximus executed her converts, including the empress, and ordered that Catherine herself be put to death on a spiked wheel.

She became patron saint of libraries and librarians, as well as teachers, archivists, and all those associated with wisdom and teaching, and all those whose livelihoods depended upon wheels.