No gentlemen are bankers

Pure logic, according to Ernest Nagel (and James Newman) at least. In the classic book on Gödel's theorem the following example appears:

Where g stands for gentlemen, p for polite, and b for bankers, with the bar on top meaning not. So gentlemen are contained in polite, bankers are contained in not-polite, so it follows that gentlemen are contained in not-bankers. Of course you can substitute polite with other epithets. But they got it right. As I said, it's pure logic.