Knowing when to double is probably the most difficult aspect of backgammon. To try to give some guidance on this topic I am going to introduce you to

"Woolsey's Law". (Kit Woolsey is an American backgammon master and leading theoretician.)

The key to Woolsey's Law is to realise that there are three possible answers to the question: "If I double, is it a take for my opponent?" They are:

1. Yes, I'm absolutely sure it is a take.

2. No, I'm absolutely sure it is a pass.

3. I'm not 100 per cent sure.

Ignoring the first two categories for now, Woolsey's Law of Doubling states: "If the answer falls into category (3) then it is always correct to double." Let's see why the rule works:

Maybe the position is a pass. If you have failed to turn the cube when your opponent's correct action is to pass, then you may cost yourself considerable equity.

Perhaps your opponent will think it is a pass. Backgammon is largely a matter of judgement and your opponent's evaluation may be radically different from your own. Most players are pessimistic about a position when they are losing and often pass when taking is the theoretically correct action.

Maybe it is a correct double and a correct take. The majority of early game doubles are also takes and therefore your action is likely to be correct.

The worst case is if your double is incorrect and your opponent correctly takes. This is unfortunate but by no means the end of the world. Unless you have completely mis-evaluated the position you are likely to have an edge and be the favourite. You have forfeited future use of the cube to your opponent but you are playing for doubled stakes with an advantage - how bad can that be?

When Woolsey first discovered this law and began applying it he saw a tremendous improvement in his results. He began winning doubled games and gammons where previously he had been waiting too long and only collecting single points, so he was winning approximately the same number of games but his equity per game increased dramatically.

Doubling theory is the most complex area of the game but the application of Woolsey's Law can make life a little bit easier - it also leads to games with high cubes!

I shall give a practical example of all this in my next article.

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