Mary: Okay let's look at the facts as we know them. Fact: He said he was going to the library.
Lucy: Fact: He never goes to the library.
Mary: Fact: He stayed out all night long.
Lucy: Fact: He was probably with a girl.
Mary: Ok... that's not a fact but it's a safe guess; let's just assume. Assumption: He spent the night with the girl.
Lucy: Assumption: He made out with her all night long.
Mary: Fact: You are way too young for me to be playing this game with you.