From Costanza's original thread (entire text):
This is for anyone in the LessWrong community who has made at least some effort to read the sequences and follow along, but is still confused on some point, and is perhaps feeling a bit embarrassed. Here, newbies and not-so-newbies are free to ask very basic but still relevant questions with the understanding that the answers are probably somewhere in the sequences. Similarly, LessWrong tends to presume a rather high threshold for understanding science and technology. Relevant questions in those areas are welcome as well. Anyone who chooses to respond should respectfully guide the questioner to a helpful resource, and questioners should be appropriately grateful. Good faith should be presumed on both sides, unless and until it is shown to be absent. If a questioner is not sure whether a question is relevant, ask it, and also ask if it's relevant.
Meta:
- How often should these be made? I think one every three months is the correct frequency.
- Costanza made the original thread, but I am OpenThreadGuy. I am therefore not only entitled but required to post this in his stead. But I got his permission anyway.
As I understand it: If you draw out events as a DAG with arrows representing causality, then A acausally effects B in the case that there is no path from A to B, and yet a change to A necessitates a change to B, normally because of either a shared ancestor or a logical property.
I most often use it informally to mean "contrary to our intuitive notions of causality, such as the idea that causality must run forward in time", instead of something formal having to do with DAGs. Because from what I understand, causality theorists still disagree on how to formalize causality (e.g., what constitutes a DAG that correctly represents causality in a given situation), and it seems possible to have a decision theory (like UDT) that doesn't make use of any formal definition of causality at all.