Free Will and Retrocausality

I discussed yesterday's post on retrocausality with a few people and thought I'd make a quick post to explore an analogy that shows what a successful demonstration of the phenomenon would really mean for free will.

Some of you may be geeky enough to remember the Fighting Fantasy books - one incarnation of the 'choose your own adventure' concept. For those who aren't familiar with them, the books are divided into paragraphs (usually a few hundred) which are numbered; after reading one, you're offered a choice of which paragraph to read next to continue the story. Some choices lead to an ignoble death, some lead to the eventual solution.

When you read a paragraph (let's say #150), you take the information in it, plus any previous information you know, and make a decision on which paragraph to read next (we'll say #200 or #60). In fact it's probably fair to say that you pick the option that seems most sensible - given what you know (i.e. the past). That's analogous to any other decision-making moment. If you'd taken a different route through the story to reach #150, you might know that paragraph #60 means certain death - so you'd pick the other option. You do make a 'real decision'. (In reality, unlike Fighting Fantasy, you can't go back and start again, so you only make one decision in practice - this is really what determinism means.)

Now let's introduce retrocausality. This is very easy to include in our Fighting Fantasy analogy - you can just cheat. You glance ahead, read #60, realise it'll kill you, and go back and pick #200 instead.

What may not be so obvious is that back-in-time signalling has exactly the same effect. The signal from the future changes the information you have, so your decision changes. There's no paradox, because at the time you received your signal from the future, it accurately described what the future would be. However, now knowing that, you can deliberately pick a 'different future'. (It's not even a problem that the future where you sent the signal back is now probably not going to happen - although the explanation of that is more complicated.)

This is really the key distinction between determinism and fatalism, so I'm quite excited about it - if we can really send retrocausal signals, we should be able to thoroughly put the latter to rest.