We’re currently watching BBC’s Sherlock Holmes and enjoying it immensely. The character of Sherlock is so well done that it keeps you captivated for the entire show, just as the books did in my teens. Of course, such a striking character is just begging to be typed in our favorite non-scientific personality system, the Myers-Briggs system. (The fact that it’s non-scientific isn’t of great concern; it merely means that it’s not repeatable when used on real people, but that doesn’t reduce the usefulness of its categories for self- and other-analysis in a general sense.)
I’ve seen claims that Sherlock is a primary Ti user. Until the episode The Hounds of Baskerville, I could see this argument, because we didn’t know exactly how Sherlock’s thinking process worked. But in the Baskerville episode, his thinking process is shown clearly (when he’s trying to put together Liberty, In, and Hound), and it’s not introverted thinking–which would be a logical process deriving one thing from another to get to a sound conclusion–but rather introverted intuition, trying many possibilities until everything converges into one answer.
There are arguments that his logical explanations for his uncanny knowledge preclude him from using introverted intuition. However, this is mixing up the external presentation (his explanations) and the internal process (how he comes to his conclusions). Ni-dominants can’t describe the actual thought process that leads to their conclusions, because it’s something more akin to crystallization, where an atom falls into its natural position in a lattice and you just know. So after many years of living this reality, they develop the ability to explain themselves through their secondary, extraverted function, which helps them come up with an alternative path one could use to get to the same conclusion, using objectively accepted frameworks. It’s a mistake to confuse the external presentation of the thought process with the actual internal thought process.
In fact, the clearly ordered, logical explanations that Sherlock offers are actually evidence that he’s using Te, not Ti. Ti is very logical and orderly internally, but externally Ti dominants aren’t nearly so ordered. Having had long conversations with a couple INTPs, you quickly realize that A) they talk a lot when you get them on a topic of interest, and B) they never get right to the point. They either wander off on one tangent after another, never to return, or they travel all over the world to finally come back and conclude their point, which has now been firmly founded on an exploration of every possibility and how it all fits together. Sherlock doesn’t worry about other possibilities (to any great extent). He has his conclusion and his explanation is concise, giving the impression that it’s the only possible path you can take.
I’ve also seen arguments about Sherlock’s turbulent emotions, which are offered as evidence that he uses Fe. This again is contradicted by experience with INTPs and ENTPs. xNTPs have a personableness to them–they’re friendly, though with some social awkwardness. INTPs are much more self conscious and awkward, but still have a noticeable warmth to them. ENTPs are actually compellingly warm if you are the focus of their interest at all–you’ll only realize that they aren’t Fe primary when someone they aren’t interested in starts talking about something they don’t care about–they’ll suddenly just drop out of the conversation entirely. Sherlock isn’t warm at all, but you clearly get the sense over time that he’s good. It takes some time to realize it because it’s internal, an internal value system, or Fi. The turbulence fits quite well with this, because he has no problem being emotionally turbulent around strangers–something that Fe users won’t easily do. Fe can be turbulent, but only with those who are close. Strangers will generally enjoy the warmth of Fe from those who have it.
Finally, there’s the question of Se, which clearly plays a big role. I’ve seen him typed as ESTP because of the role Se plays for him. I think that’s a compelling argument, but after thinking about it I don’t see him with Ti or Fe, and I can see both Te and Fi. Further, I’m not concerned about the fact that he feels a need to experience the case in order to understand it, because I’ve seen that same process with an INFJ: intuition leads to a vision, but the vision has to be experienced to really understand it. It shouldn’t be surprising, really, because dominant Ni is fed by the inferior Se in order to have the material to make its convergent vision from. This is clearly how Sherlock uses Se. However, he does seem to use Se much more strongly than you’d expect for someone with inferior Se, and I’d argue that that is the fantasy about Sherlock’s character, that’s what makes him fiction. There’s no one (or at least, almost no one) who is truly like Sherlock in the real world, and that’s because real people with inferior Se almost never have it developed like he does. That’s his magic.
So in case it’s not obvious already, I think Sherlock is clearly an INTJ, although a fantastical version of it.