Forum Archive : Rules

Jacoby rule ambiguity?

From:   Chuck Bower
Date:   8 March 2011
Subject:   What actually IS the Jacoby Rule?
Forum: Forums

Tom's site is the first place I go to find definitions:

    "Jacoby Rule:  [Named for Oswald Jacoby, who proposed the rule.]  A
    rule popular in money play which says that gammons and backgammons
    count only as a single game if neither player has offered a double
    during the game. The Jacoby rule is not used in match play. The rule
    speeds up play by eliminating situations where a player avoids doubling
    so he can play on for a gammon."

Is this definition accurate?  I'll give a hint: what if there is an
automatic double?

Jacoby Rule (my wording):

    The multipliers (x2 for gammon, x3 for backgammon) shall be used if and
    only if:

    A) the doubling cube has increased in value by any means, or

    B) the doubling cube has been offered and accepted.

    You must choose one of (A) or (B). Which one?

- Books by Paul Magriel (1976) and Lewis Deyong (1977) imply A.
- Books by Philip Martyn (1976), and Jim and Mary Zita Jacoby (1973) (son
  and wife of Ozzie) say B.

The tiebreaker (and trump card?) 1969 book by John Crawford and Oswald
Jacoby (credited by all with the rule) says (in Chapter 16 ... Variations
of Play):

    "Some people play the Jacoby rule as long as there has been no regular
    double (as opposed to automatic doubles); we prefer to play it only
    when the cube is at 1."

OTOH, maybe Jacoby's wishes can/should be overridden by

Casper van der Tak  writes:

Gammons and BGs don't count before the first cube turn. An automatic double
means that the cube starts on 2, 4, whatever, but it is not turned yet. I
did not check the formulation, but probably the Jacoby rule could be best
worded as that gammons and backgammons don't count with the cube in the

Sam Pottle  writes:

B seems obvious to me, but I recognize that others may not agree.

Steve Mellen  writes:

I think I need to know what they actually wrote before I know if there's an

I think most people would see (B) as the more natural answer. But if you
actually think about the purpose behind the Jacoby Rule -- which I might
paraphrase as "let's not waste a lot of time playing on for a gammon with
the cube on 1" -- I think (A) is the more logical answer. If someone can
suggest a different purpose for the Jacoby Rule that makes (B) the more
logical response, I'm all ears.

Chuck Bower  writes:

As far as the definitions by Magriel and Deyong in their books, here is
verbatim what they say:


    "Players can agree before the game begins that gammons and backgammons
    will count only as 1 point if the cube has not been doubled by a player
    during the course of the game."


    "The Jacoby Rules prohibits either player from wining more than 1 point
    in a game unless the cube has been turned."

It's far from obvious either of these even consider automatic doubles. I
interpreted the specific number '1' in each to indicate automatics would
negate the rule, but that might not be the proper interpretation,
particularly for Magriel's where he may have been referring to the
gammon/backgammon multiplier being 1. But for the most part I don't think
they recognized the ambiguity/confusion that I bring up.

Jacoby-Crawford (as quoted earlier) and Martyn explicitly mention automatic
doubles and how they affect the rule (and the two books take the opposite
view). Jim and Mary Zita say "... Unless a double has been made and
accepted, either player can concede a single game at any time."

Pragmatically, IMO, unless you know how your opponent interprets the rule
it should be discussed beforehand when you are playing automatics.
Did you find the information in this article useful?          

Do you have any comments you'd like to add?     



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