Your definition is a contradiction. Given X is an ordered-set element with ordinal number n iff not-X is an ordered-set element with ordinal number m>n, therefore if not-X is an ordered-set element with ordinal number m, then not-not-X = X must be an ordered-set element with ordinal number n>m, therefore n>m>n, therefore n != n. 

It's also a mis-paraphrasation of Hume, who describes a sound, although rough, probabilistic heuristic for guessing whether an alleged event transpired, not a definition of any kind. 

See the relevant [SEP](https://plato.stanford.edu/entries/hume-religion/#Mir) article.