Variables are ... well, "things that vary". So in the language surrounding 
iteration, I'm not saying "variable X occurs before Y". I'm saying X and Y take 
on values *before* an iterate. And they take on values *after* an iterate. Then 
ΔX and ΔY may be non-zero. I.e. x1, x2 ∈ X and y1, y2 ∈ Y and the iteration 
looks like Iter(x1,y1) → <x2,y2>.

In this context, X is not a cause of Y. Iter() is a cause of the variation in X 
and Y.

What Frank said was that the variation in X might be *predictive* of the 
variation in Y. So, even if you don't know the values y1 and y2, you can "get a 
feel for" y1 and y2 by looking at x1 and x2.

Re: "latent variables" - Iter() might be defined in terms of 3 variables, X, Y, 
and Z. And we might have access to X and Y, but not Z. (I.e. we know the values 
x1, x2, y1, and y2. But we don't know the values z1 or z2.) It's possible that 
X be predictive of Y whether or NOT X and Y depend on Z. But if they do depend 
on Z, then we might be able to go beyond merely "predictive of" and say 
something about causality ... e.g. we might be able to say something like Z 
causes both X and Y, which would then explain why X and Y correlate.

I hope that helps.

On 11/30/21 4:10 PM, [email protected] wrote:
> My problem is, of course, that if variable X occurs before Y and is 
> predictive of it, then it is a cause, by definition.  I am groping for an 
> understanding of a “latent” variable.  I promise I am not arguing, here. 

-- 
"Better to be slapped with the truth than kissed with a lie."
☤>$ uǝlƃ


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