Wednesday, December 13, 2006

Train of Thought

Customer Service Centre
South West Trains
Overline House
Blechynden Terrace
SO15 1GW

Dear Sir/Madam,

I am writing to draw your attention to this picture that I took at Kingston station recently. As you can see, the sign reads “We regret that owing to a fault no information can be displayed at present”. This is confusing because this statement is itself information, so therefore the information that the sign is displaying (that it cannot display information) is incorrect.

By displaying the information that it cannot display information this sign represents a paradox – in fact, a dot-matrix version of the liar paradox that dates back to Greek philosopher Eubulides of Miletus in the fourth century BC. Another example of the liar paradox is “This statement is false”.

Perhaps you are employing paraconsistent logic and believe that the statement can be both true and false. Or maybe you are using situation semantics whereby the “negation liar” statement can be false without contradiction. Or perhaps your employees have to spend most of their time making the trains run rather than engaging in philosophical discourse. They obviously didn’t have that distraction in Ancient Greece.

May I suggest that you reword the sign to read “We regret that owing to a fault no information can be displayed at present (apart from this bit of information, obviously)”. You may have to replace your dot-matrix displays across the network with ones that have an extra line each, but that would be a small price to pay for logic. (I feel that putting the part in brackets on a separate line that you scroll up to would confuse matters further.) This will then not perplex any passing philosophers, and thus not cause them to miss their trains when they begin to question whether the 18:49 to Waterloo actually exists anyway.

Yours faithfully,

Salvadore Vincent