What is an MBTI introvert? Someone who gets their energy from within. Now Mycroft was an introvert, for the whole point of the Diogenes Club was to have a place where people can avoid talking with the unwashed peons. But is it so clear that Holmes is an MBTI introvert? When left alone, instead of being energized, Sherlock Holmes becomes moody, bored, and fidgety. He indulges in opium for he would do anything to distract his mind from the tedium. Holmes becomes greatly energized when he is out on the hunt. Watson often remarked about the great change that took over Holmes when he was out and about sniffing for clues like a bloodhound. He would become oblivious to everything around him. Now if he was such an introvert, he would have found just as much pleasure staying inside, and analying a case from a purely theoretical perspective, but he greatly preferred getting his hands dirty. He was an extrovert since his energy came not from within, but from outside himself. This also helps to answer the following question: Was he a sensor or an intuitive?
What is an MBTI intuitive? One who prefers the abstract, and general over the tangible and the specific. Sherlock Holmes was a fiend for details. That was his obsession. If he let the slightest detail escape him, he would greatly reprimand himself. Although he used both inductive and deductive reasoning, he had a marked preference for inductive reasoning when it came to solving cases. He went in this order: inductive reasoning followed by deductive. He would look back on previous cases, and use the specific details of a past case in order to make a generalization (inductive) and then he would apply it to the case at hand (deductive). If he were an intuitive, he would have shown a preference for using deductive reasoning first. However, he used the specific details of his past experiences and inductive reasoning first.This combined with how much he loved to get his hands dirty indicates to me that he is a sensor.
Now, about F or T, I am not so sure. Sherlock Holmes liked to think and analyze therefore he must be a thinker, right? Of course not. What is an MBTI feeler? Feelers prefer ethics to make the decisions, while thinkers prefer logic. The funny thing is both methods can be subjective. A thinker could easily be too selective with his facts and make a logical but partial conclusion. Holmes was guided by principles and ethics, and this was what kept him from becoming Europe's greatest villain. If he was a thinker, he would have tried being the villain out of pure intellectual curiosity, but his ethics always held him back. This one is inconclusive to me, so I'm not sure if he was a thinker or a feeler.
P or J. J's like rules, while percievers like freedom. Right? Wrong. What is MBTI Judging? A judger is someone who uses their T/F axis to relate to the outside world, while a perciever uses their S/N axis to relate to the outside world. Holmes was a boxer, no slouch with a gun, and quite adept at wielding fire pokers or hunting crops when it came time to open up a can of ass whooping. His senses were keen, and this is how he related to the outside world when solving a case. Conclusion: His P'ness was long, thick and conspicuous without a doubt.
Sherlock Holmes was an ESXP if we use strict MBTI definitions. This is far from the biased INTX conclusions that people usually arrive at.