[mindviews]

We should be talking about "consistency" being the fundamental idea, not causality. I think "retrocausality" is an especially distracting choice of words.

I find the clearest way to think about this is in terms of Feynman Diagrams. Here's a quick intro to some of the rules: http://bolvan.ph.utexas.edu/~vadim/classes/2008f.homeworks/Q... If you're not familiar, ignore the math and just look at the pictures on the first couple of pages.

Take a simple diagram of a photon interacting with an electron (google QED Vertex). Here's a very tiny ASCII version: ~< The squiggly line represents a photon propagating and the straight line segments (which should have arrows pointing a direction) represent an electron propagating. We can rotate this thing around in a bunch of different ways in time so that we have 1 or 2 inputs ("before") an 2 or 1 outputs ("after") in time. For example, with time going left to right, ~< represents a photon decaying into an electron and positron. Flipped around, >~ represents a electron and a positron colliding/annihilating to create a photon. Turned another way you could have a photon and electron as input, and an electron with a changed momentum as the output. For the last case you could say the electron absorbed the photon. But really, these are all the exact same pattern just rotated around in spacetime. So, what is causation? If it's all the same pattern, it's clear that consistency with the pattern is more important than the direction of time's arrow.

Speaking very loosely now (there are a bunch of constraints and caveats on what I'm about to say), you can plug these diagrams together to make arbitrarily complicated internal structures. But if they have the same inputs and outputs, they are in a sense consistent. And if you do it just right you can constrain which types of patterns can link up with the one you've set up. So, in the end, only patterns that are consistent with your setup can happen. Which is pretty much what this article is describing.