From "The Art of Manliness".
How do you know if a girl likes you? Well, you ask her out. If she says yes, she probably likes you. If she makes up an excuse to not go out, you have to invoke the Brad Pitt Rule. Here goes. Would she cancel those plans if Brad Pitt were to call and ask her out. The answer, of course, is yes. Therefore, if she says she's too busy, it's because she doesn't want to go out with you.
Brilliant and concise.
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