 [w]e might, for instance, express negation not by inserting a word “not”, but by writing what we negate upside down. Such a symbolism is only inconvenient because we are not trained to perceive complicated symmetry about a horizontal axis, and if we adopted it, we should be rid of the redundant “not-not”, for the result of negating the sentence “\(p\)” twice would be simply the sentence “\(p\)” itself. (F.P. Ramsey 1927, 161–2)