Sherlock is a thinker and an observer; his incredible ability to notice and draw deductions from seemingly trivial details is his main tool for solving crimes he investigates. He also often utilises his "mind palace", a tool for remembering the smallest of details and organising his memories in a visual way. However, his unusual and somewhat anti-social personality has led to many in the official police force distrusting and disliking him. Sherlock claims on more than one occasion to be a "high-functioning sociopath". However, according to Jim Moriarty, as well as Sherlock's own actions and displays of emotion and empathy, this may not be true. Sherlock does not seem to exhibit any of the symptoms of an anti-social personality disorder. John jokes once, in order to explain Sherlock's behaviour, that he might suffer from Asperger's Syndrome, a disorder related to autism, though this has never been confirmed.
Sherlock has many well-developed abilities that aid him with his detective work, including a profound aptitude for deductive reasoning. Upon meeting a person, he will often "scan" them, using elements of their appearance to arrive at astonishingly accurate conclusions about their past or personality. However, Sherlock is not infallible, as he admits "there is always something" that he misses or misinterprets.
He often uses a memory retrieval technique called "the method of loci", which he refers to as his 'mind palace'. John describes this system of storing memories as plotting them on a map of a familiar location, and retrieving those memories by finding the way back to them, so as to theoretically never forget anything. To use this skill, Sherlock requires silence and space to himself to reduce outside interference.
Sherlock has also proven incredible espionage talents. Despite not having spoken to Irene Adler for months, Sherlock was able to follow her to Pakistan, pose as her executioner and save her life, keeping this a secret from (possibly) everyone.
He also shows great skill in both armed and unarmed combat. In reference to his Conan Doyle counterpart, the rules of the combat discipline Baritsu hang over his bed. He often uses his deductive reasoning to identify weaknesses of his opponents before he strikes them, only losing in fights when he is taken by surprise.