ME: So, what's the difference between a good argument and a bad argument?
STUDENTS: Good arguments are supported by facts.
ME: So here's an argument. There's an invisible unicorn in this room. What's my reason for saying this? That you can't see it.
STUDENTS: They have to be relevant facts.
ME: But if the claim is about invisible unicorns, whether you can see them is definitely a relevant fact. So I've supported my conclusion with facts. Does that make it a good argument?
[All this as a preamble to discussing logic.]
