The brilliant philosopher David Hume remarked that if two events are always foun

Question

The brilliant philosopher David Hume remarked that if two events are always found to be correlated to each other with one event happening prior to the other, we call the earlier event the cause and the latter event the effect. However, it has been pointed out that two events can be correlated, with one happening after the other, but only because they both have the same common cause, and not because of any direct causation. It's not "post hoc, ergo propter hoc".

What stops me from defining a new verb "retrocause"? It works just like Hume's definition, but only in reverse. We note the presence of a broken egg is always correlated perfectly (or very very nearly so up to an exponential degree of accuracy. Loschmidt reversal, anyone?) with the existence of an unbroken egg in its past. So, we say broken eggs retrocause unbroken eggs. In the same manner, unbroken eggs retrocause hens laying eggs. And hens retrocause female chicks. And female chicks retrocause hatching eggs. And so on and so forth.

In delayed choice experiments, what stops us from saying the choice of apparatus settings retrocause the preferred basis of a quantum system in its past?

What distinguishes causality from retrocausality?

Explanation / Answer

What distinguishes causality from retrocausality? The laws of physics are pretty much time-symmetric so it seems the two should be not too different. However, we all know that causality goes from past to future. This is a question that many have worked on and none have fully resolved. For an overview, there are a couple of pages on Wikipedia: Arrow of time and Entropy (arrow of time). It seems the best answer so far is "it has something to do with entropy."

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