# [Retros] A simple substitution test for (retro) Conventions

Guus Rol grol33 at gmail.com
Thu Jun 12 12:35:07 EDT 2014

```Dear retro-friends,

In Mathematics, it is always a good idea to check a function by making some
simple substitutions for the variables such as 0, 1, infinity, pi or e. It
will tell you something about the behaviour of the function and allows
you to detect a blatant error if there is one.

Fortunately, this method is not restricted to math but can also be applied
to related fields such as retro-conventions and chess laws. Lets substitute
the DGC (Diagram Game Cluster - see my previous post on conventions and
rules) by a single game and pretend that the chess laws and the
retro-conventions work on it simulataneously. Or to put in a more appealing
form: instruct all participants in a tournament to apply the playing rules
and the retro conventions simulataneously to their games and report any
conflicts to the arbiter.

The tournament gets underway and players meet their first opportunity to
castle. FIDE laws (forgive me Kevin) say they can castle and the convention
allows it as well so it is plain sailing at this point. Then we meet an
opportunity to play en passant. OK with the laws but the e.p. convention is
hesitant. Doesn't like it but must agree when the player shows his score
sheet. After all, the player is permitted to e.p. when he can prove it and
he certainly can. The games move on and some of the players consider it
time to check the logics that came with the conventional package. One
attempts to make an a posteri e.p. capture in Petrovic style but is soon
forced to retract. The chances of justifying an illegal move a posteriri
are mathematically 0 since a posteriori logic is about unlikely assumptions
but not about impossible ones. On other tables the players attempt to
construct retro variants, pRA splits and retro-strategical manoeuvres but
they all fail on the same issue: with all states known there is no way to
construct diverging paths and competing rights or restrictions. By the end
of the day all players report back that including the conventions had 0
impact on their games.

And such is in line with my previous article. The conventions and laws do
not intersect but each treat a domain of their own. The conventions are
highly significant when selecting games from the DGC but mean absolutely
nothing in connection to individual games. You may conclude with me that
this is a fairly obvious and boring result one could have seen coming for

But then there is the snake under the grass! 2 Players have approached the
arbiter complaining they had issues over the 3R and 50M conventions. Both
had chosen to play the first-to-blink game and not claim draws though they
were entitled to. These tactics were rudely interrupted by 3R and 50M
conventions demanding automatic draws. This was very interesting. Why did
these conventions have impacts on the games while the other conventions had
none? The answer is not difficult to see but has significant consequences.
These conventions are not merely trying to fill in information holes -
another way of describing selections from the DGC - but they are amending
playing rules as well!

There is still quite a lot more to say about 3R and 50M and so this a good
point to sign off and leave it till another post. If the preceding exercise
has made you somewhat suspicious of these 2 conventions, then I am glad to
have achieved my objective for this one.

Best wishes, Guus Rol
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