Why mathematicians and philosophers ought to be banned from pubs...

From the November 6th times letters page at: http://www.timesonline.co.uk/article/0,,59-882044,00.html

Flipping marvels
From Mr Dennis Orton

Sir, Beermats will now flip more accurately (report, November 3). I also think they should have something interesting written on them.
When teaching (Bertrand) Russell’s Paradox I often suggested a beermat with on side A: “The statement on the other side is false” and on side B: “The statement on the other side is true”.

Yours faithfully,
DENNIS ORTON
(Head of mathematics, The Portsmouth Grammar School, 1977-96),
Spring Cottage, 5 Weston Lane,
Weston, Hampshire GU32 3NL.
November 4.