The Master notes that his faculty of observation and facility for deduction was due, in part, to systematic training. He thoughtfully adds, "My ancestors were country squires, who appear to have led much the same life as is natural to their class. But, none the less, my turn that way is in my veins, and may have come with my grandmother, who was the sister of Vernet, the French artist. Art in the blood is liable to take the strangest forms."

Thus it is that he turns his "art in the blood" towards the arts and sciences of deduction. Among the more prominent of these arts are Tracking, Handwriting Analysis, Cryptography, Studies upon Paper & Watermarks, and Tobaccana (which is analyzed elsewhere on this site).

In addition, Holmes made a small study of opening locks by nefarious means. In GREE, the inspector notes "the clever way in which [Holmes] had forced back the catch.