*For a more parable-ic version of this, see here.*

Suppose I make a precommitment **P** to take action **X** unless you take action **Y**. Action **X** is not in my interest: I wouldn't do it if I knew you'd never take action **Y**. You would want me to not precommit to **P**.

Is this blackmail? Suppose we've been having a steamy affair together, and I have the letters to prove it. It would be bad for both of these if they were published. Then **X**={Publish the letters} and **Y**={You pay me money} is textbook blackmail.

But suppose I own a MacGuffin that you want (I value it at £9). If **X**={Reject any offer} and **Y**={You offer more than £10}, is this still blackmail? Formally, it looks the same.

What about if I bought the MacGuffin for £500 and you value it at £1000? This makes no difference to the formal structure of the scenario. Then my behaviour feels utterly reasonable, rather than vicious and blackmail-ly.

What is the meaningful difference between the two scenarios? I can't really formalise it.