User blog comment:Moooosey/Simple psi-- a fairly simple ocf/@comment-43798125-20191026225036/@comment-35470197-20191027104358

@Moooosey

> ordinals need to be emulated because they aren't computable? (At least, they aren't computable in the strictest sense)

Exactly. By the definition of the computability using Turing machines or equivalent computation models, we are not allowed to use infinite ordinals in order to define a computable function. Such a function can be occasionarily computable in the sense that there can be an (unspecified) Turing machine which immitates it, but such a "optimistic possibility" does not ensure that we have defined a computable function unless we show the computability.