Published online by Cambridge University Press: 12 March 2014
In [2] we constructed an infinite set of natural numbers containing nosubset of higher (Turing) degree. Since it is well knownthat there are nonrecursive sets (e.g. sets of minimal degree) containing nononrecursive subset of lower degree, it is natural tosuppose that these arguments may be combined, but this is false. We provethat every infinite set must contain a nonrecursive subset of either higheror lower degree.
This work was supported by National Science Foundation Grant GP8866.