Preferential entailment

Okay kiddo, let's imagine you have a secret club with your best friend. In your club, you only let in people who have a certain toy. Let's say it's a special red ball. So if someone has the red ball, they can be in your club. But if they don't have the red ball, they can't be in your club.

Now, let's say your friend has a blue ball. Well, that's not the red ball you wanted, so she can't be in your club. But then your other friend comes and has both the red ball and the blue ball. Well, because they have the red ball, they can be in your club. But because they also have the blue ball, they can also be in a another club that only lets people with blue balls in.

That's sort of what preferential entailment is. It's when you have one rule (like only letting people in with the red ball) but then also have another rule (like letting people in with a blue ball too). So if someone meets both rules, they get to be in both clubs or satisfy both conditions.