 Such classifications illustrate how the position of a set within \(\mathcal{D}_T\) can be understood as a measure of how far away it is from being computable—i.e., of its degree of unsolvability or difficulty. However unlike other conventional measurement scales, the structure of \(\mathcal{D}_T\) is neither simple nor is it always straightforward to discern. Some evidence to this effect was provided by the fact that the answer to the following question was posed but left unanswered by Post  (1944):[27] 