Use the term ipso facto when the very fact that something exists or occurs means that something else is true. For example, if you're born in the United States these days, ipso facto you have a Social Security number.
Ipso facto literally means "by that very fact" in Latin, and it's often used in legal documents, although writers, philosophers, and scientists use it too. The writer Norman Mailer once said, "If you grow up in Brooklyn, you’re a New Yorker ipso facto." In other words, the fact that you live in a borough of New York automatically means you're a citizen of that city.