Several years ago, a male colleague and I left a meeting on one side of campus at the university where we both teach to return to our offices, a 15-minute walk away.

Since I had driven my car to the meeting, I asked my colleague if he’d like a ride back.

After an almost imperceptible hesitation, he politely thanked me and said no.

Walking to my car, I suddenly realized I’d just had my first encounter with the “Billy Graham rule,” a concept highlighted in recent news as a result of reports of Vice President Mike Pence’s longstanding principle of not having meals alone with a woman or attending events serving alcohol unless accompanied by his wife.

The rule, famously articulated by the evangelical minister Billy Graham, is basically a guideline that says men and women should not meet alone, whether in offices, or cars, or other places in order to avoid illicit temptations or appearances of impropriety.

It’s been adopted by other evangelical pastors and leaders (a history of its origin is here): The late founder of the evangelical university where I work was known for saying that he’d pass by a female member of his church walking in the rain if he were alone in his car to avoid the appearance of impropriety.

Once I realized why my colleague had turned down my offer, I felt a twinge of embarrassment and awkwardness, as though I’d invited him to a game of strip poker instead of a three-minute ride to the other end of campus.