Object: envelope that is addressed, a postage stamp (don't put stamp on envelope yet)

Good morning, boys and girls. I want you to pretend with me for a moment. Let's pretend I'm going to have a really big party, and I wanted to invite you. How would I send you the invitation? That's right, I'd mail you the letter. Okay, here's my envelope, and I've got your address on it, and I'm all ready to send it out, right? Can I send the invitation out like this? No, I can't. You know why not? It doesn't ha…