What is Frege's "Concept horse Problem" ?

I argue that Frege's so-called "concept 'horse' problem" is not one problem but many. When these separate sub-problems are distinguished, some are revealed to be more tractable than others. I further argue that there is, contrary to a widespread scholarly assumption originating with Peter Geach, little evidence that Frege was concerned with the general problem of the inexpressibility of logical category distinctions in writings available to Wittgenstein. In consequence, Geach is mistaken in thinking that in the Tractatus Wittgenstein simply accepts from Frege certain lessons about the inexpressibility of logical category distinctions and the say-show distinction. In truth, Wittgenstein drew his own morals about these matters, quite possibly as the result of reflecting on how the general problem of the inexpressibility of logical category distinctions arises in Frege's writings , but also, quite possibly, by seeing certain glimmerings of these doctrines in the writings of Russell