How about something like this as a definition: There is a "status quo", an outcome for each agent if neither takes any special action, that serves as reference point. Agent B is blackmailing A if s/he announces to A that the status quo is no longer a possible outcome, and the possible outcomes (relative to the status quo) have utilities either "-x for A, +y for B" or "-z for A, anything for B", with z > x. (ETA: typo that said A instead of B corrected in the last line.)

I don't think it is possible to define blackmail withou... (read more)

So is robbery blackmail? "The status quo is not to harm or steal. Give me your money, or I will hurt you and take your money." Wouldn't most crimes fall under the same definition?

In fact, isn't the social threat of negative publicity just blackmail against would-be public adulterers? "-affair for A, +prudish satisfaction for Bs" or "-status for A, whatever Bs get out of shaming A". And justice is probably just blackmailing people into being nice against the status quo of natural selection to avoid punishment...

0Stuart_Armstrong7yYes, I'm having great trouble defining blackmail without a status quo...

Duller blackmail definitions

by Stuart_Armstrong 1 min read15th Jul 201346 comments


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.