-- John H. Watson, "The Greek Interpreter"
It wouldn't be until the early 1900s that we'd get the phrase "nature versus nurture," but the question was plainly on the Victorian minds when we first get to meet Sherlock Holmes's best argument for the "nature" side: his brother. Of course, the opening paragraphs of "The Greek Interpreter" have some pretty strange thoughts on Watson's fellow man, so we might want to mull over that opinion a bit. Especially after Watson had written the words:
"This reticence upon his part had increased the somewhat inhuman effect which he produced upon me . . . ."
For a doctor, and as such, a student of the human condition, John Watson seems just a little freaky about his room-mate in that sentence. He goes on to call Holmes "an isolated phenomenon," basically a freak of nature, unreproducible in the species. It's weird to think of anyone describing their closest friend in such alien terms as "inhuman," and makes one wonder a bit about Holmes and Watson's relationship, and if Watson might have been putting on a good front in most of the accounts of their time together.
It definitely seems to come as a relief to him when a second Holmes shows up, who seems even more alien than the first with his weird club of silence. For us, "The Greek Interpreter" is almost like a mini A Study in Scarlet, as we are introduced to a new pinnacle of human observation skills. If Sherlock and Mycroft had taken Watson back to their home planet to introduce him to the rest of their kind after this case, one might not even be too surprised. (And my money is on Coluan rather than Vulcan for that alien race. Just saw one on last night's TV schedule.)
When Mycroft tells Sherlock that he had expected his brother to come 'round on the Manor House case, we get an inkling that the younger Holmes has used the elder the way Scotland Yard uses him. The hierarchy of intellect seems to have at least three levels in crime-solving (we can probably assume a fourth level in the beat constable or victim who comes to the Yard), and Mycroft's existence makes one even start to dream of yet another above him -- something we finally saw when Eurus Holmes strolled onto the BBC Sherlock stage.
Was there a better-than-Mycroft member of the Holmes clan before Eurus? It surely wasn't Sherrinford, the oldest sibling that Baring-Gould championed. He seemed to disappear into the life of a country squire. Old Sherrinford might have even been more to Watson's taste than the others, given that "inhuman"comment.
But just as Sherlock once said "it is always a joy to meet an American," it is always a joy to meet a member of the Holmes family for the first time, and our first encounter with "The Greek Interpreter" is definitely a joy to be had, and remembered in a re-reading, over and over again.