

If correlation doesn’t imply causation, then what does? - psykotic
http://www.michaelnielsen.org/ddi/if-correlation-doesnt-imply-causation-then-what-does/

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baddox
I confess that I only skimmed the latter 75% of the article, but it seemed
like the author is ignoring a more fundamental issue: what does it even _mean_
for something to cause something else? In so many cases, we humans assume a
rather trivial obvious definition: X causes Y if X happens before Y and Y is
extremely likely given X. Other stipulations may be assumed, like X
dramatically increases the chances of Y, or Y rarely happens without X
happening previously.

All of these intuitive definitions are useful for everyday language (smoking
causes lung cancer, drunk driving causes traffic accidents, exercise causes
weight loss, etc.), but if you think a bit deeper it seems like something is
missing. Why does it sound silly to say that marriage causes divorce,
hospitals cause deaths, graduating from high school causes college dropouts,
etc.?

I'm convinced that a precise definition of causality doesn't really exist, or
at least that there isn't one that can be usefully applied both to everyday
language and formal mathematical/scientific/philosophical language.

~~~
msellout
To me, causality is less important than simple prediction. Determining cause
is a philosophical question somewhat like asking if machines can truly think.
If a system behaves as if it contained a causal process (ie. it is
predictable), then whether or not one event truly causes another is
irrelevant.

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elchief
Correlation is a necessary, but not sufficient condition for causation. If a
is correlated with b, it means a might causes b, but you don't know for sure.
Some dum-dums think that if a is correlated with b, then it cannot cause b.

in order to show causation, you need to go back in time and change things.
This is called a counter-factual. Obviously we cannot do this. the best we can
do is to control everything as closely as possible, changing only one factor
at a time, or at least thinking we do. This is called the scientific method.

Basically, you cannot really ever prove causation, but you can provide
overwhelming evidence, along with isolated control over changing factors.

Related [http://stats.stackexchange.com/questions/36/correlation-
does...](http://stats.stackexchange.com/questions/36/correlation-does-not-
mean-causation/77#77)

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Terretta
I've always heard "correlation is not causation" which makes the title less
clever. Understood the phrase to mean that while it does _imply_ causation,
fact is not necessarily so.

The article's great. Appreciate the 'Problems for the author' highlighting
gaps for thought.

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aufreak3
The article's title reminded me of this post on lesswrong - "timeless
causality" - <http://lesswrong.com/lw/qr/timeless_causality/> \- also based on
Judea Pearl's work.

