User blog comment:Kyodaisuu/English description of Fish numbers/@comment-25418284-20131102173245/@comment-24061664-20131104005404

@Deedlit11

I don't understand your point. If you say that Rayo's function cannot be defined, how about busy beaver function? If you say that busy beaver function cannot be defined, then you should also deny Xi function. However, you say that Xi function is stronger or something like that, so you already admitted that Xi function can be defined. Why busy beaver function and Xi function can be defined and Rayo's function cannot be defined?