(That is—with ‘2^\(n\)’ representing ‘2 to the power \(n\)’—‘[2^(2^(2^(2^(2^2))))]\(+1\) is prime’; cf. Tennant, 1997 p. 152.) They cannot deny the sentence exists, for there is the token before our very eyes. But there are strong grounds for thinking that no concrete proof or disproof will exist, for the only methods available may use up more time, space and material than any human could have at her disposal, perhaps than actually exists. There are countless sentences with this property: concre