Posted by Mike Dennis on December 07, 2013 at 23:53:35 user MTD.
I've pulled this from the AR taught me to sail, as I think it needs a thread of its own.
I was always interested in the dowsing episode of PP as a child, but later in life became more so as I found I was able to do it. I was encouraged in this by an old friend who had strong beliefs in such things and she bought me a dowsing pendulum - it's a shame that that the practise tends to get centred on finding water when it can be used on anything (it was used in WWII for bombs etc. an Internet search will bring up numerous accounts.)
The simplest test is to use two blank postcards, write 'yes' on one of them and 'no' on the other. These are then turned over and shuffled around and the dowser has to find one of them, you can also dowse over the words and see the reaction of the pendulum to each word.
Now I realise that the second test can make you prone to 'reading' the reaction of the pendulum to fit in with what you are doing. Which brings me to a scientific explanation, and the challenge of logic in such matters.
The problem for Dick was he wanted a scientific explanation, and at the time of writing AR would have been aware (I hope!) of the importance of logic in such matters at that time due to the work of Frege and then Russell (on BBC 4 in the UK this week there has been a documentary on this subject.) What the documentary failed to mention (I suspect because it undermines the importance of logic in computing) is the work on the subject by Wittgenstein - he concluded (and I am very broadly summarising here with my limited knowledge!) that there are things in the world that cannot be explained by logic and just are, his work on this was mainly in the late 1940s in his book Philosophical Investigations, long after AR had published PP.
To return to AR the main thing I identify with Titty's dowsing in PP is how she felt afterwards, when I have done it did not upset me but I felt exhausted as if I had undertaken some physical labour!