The professor, who's name I've forgotten, asked us to consider why English schoolchildren grow up convinced that the Romans conquered Britain and their emperor said "Veni, Vidi, Vinci," meaning "I came, I saw, I conquered."
1. We trust the teachers who tell us these things, trust the institutions that taught and qualified them and the schools that employed them. We decide they're probably not out to deceive us.
2. We trust the documentation: In Latin class we would translate simplified versions of ancient passages, but of course, we translated passages about Odysseus meeting the Sirens too. Why didn't we believe those were true? Perhaps because they didn't fit our worldview, whereas the records of Roman invasion were backed up by other evidence.
3. We trust the science: We trust the archeologists who dig beneath those villas and Roman roads. We trust the carbon dating of remains. We trust the derivations of names, the histories constructed from records and remains all over the world. We don't dig out the evidence ourselves, and wouldn't know how to perform the tests, but we trust them.
If we drive and don't understand organic chemistry, if we use emails and don't understand how IP addresses work, if we eat and don't grow and breed and fertilize our own food, then we live by faith, and it's not a crutch; it's an essential part of human life.
The professor continued by saying there's two types of faith: not spiritual and secular, but rather religious and informed. The above were all examples of informed faith--we'd change what we believed if we found we were wrong. Religious faith (not a spiritual term) isn't willing to change whatever the evidence, like the girl who runs religiously every day before breakfast, come rain or shine or hurricane, and will brook no obstacles.