Holmes holds a detective He used his knowledge of science, logic, observation and experimentation. Used to always considered criminal. Although he likes to keep the results out. And a surprise to others by gradually revealing the crux of the case to know little by little and Holmes is capable of analyzing physical evidence accurately.
Well,not only holmes is intelligent and observant. His intimate,Watson,he also has it too but holmes can use his ability to solve his problems better than his intimate.Holmes likes to do the experiment and investigate.That make him have many experience skill to survive.Do you know James Moriaty? He is the first enemy of holmes.He also have observant and intelligent skills,unfortunate he use skills in wrong way.