Here's a silly conversation that demonstrates a problem in resolving cyclical dependency graphs that my wife + I had at the grocery store:

    1. Me: [looking for purchases to get in the Christmas mood] "Let's get some walnuts "
    2. Wife: [predisposed against the idea] "Let's not, we don't have a nutcracker"
    3. Me: "Well, let's get a nutcracker"
    4. Wife: "Let's not, we don't have any walnuts"

It also demonstrates the annoying ambiguity in human languages. It's ambiguous whether statement #3 is instead of #1 (my wife's interpretation), or in addition to #1 (my interpretation).