[Retros] Variables

Joost de Heer joost at sanguis.xs4all.nl
Mon Nov 24 07:09:26 EST 2008

> I haven't read the original article so I can't be sure of the role it

> assigns to the à posteriori attribute, but going by the examples I

> suspect that the AP-qualification is misused here. The role

> adaptation of the Variable is actually an exquisite example of Post

> (F)actum logic.

I don't think Stephen intended to use AP in the same sense as it is used
in retros. The paragraph that mentions 'a posteriori' is:

[Diagram B, after moves 1. Vb2-b4 Vc4-b3]
"Similarly, if White follows with 2. Ra4, this is legal only if b4 is
vacant, so again ep capture must have taken place, and if it wasn't
known before, now it is known that b3 must be a bP. This is a posteriori
justification, not prove it by doing it."

You're probably right in saying PF is a better name.


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