Professor Moriarty - Personality

Personality

Moriarty is a confident man, assuring Holmes that if he meddles in his plans, he risks inevitable destruction. He has full respect for Holmes's intellect and says that it has been an intellectual treat to grapple with him but is also completely willing to kill Holmes should he oppose him any further, showing a ruthless side. He has a fiery temper, furiously elbowing aside people in the train station when Holmes escapes him. Moriarty also has a vengeful streak, pursuing Holmes to Switzerland to kill him for destabilising his organization. Despite the vast crime ring over which he presides, Moriarty is fiercely independent. When his men fail to kill Holmes, he pursues him personally and without aid of an assistant whereas Holmes takes Watson with him wherever he goes. The only individual who appears to have Moriarty's complete confidence is his henchman Colonel Moran. He is also implied to be quite charismatic as even Scotland Yard inspectors whom Holmes respects such as MacDonald express admiration for him.

Holmes described Moriarty as follows:

He is a man of good birth and excellent education, endowed by nature with a phenomenal mathematical faculty. At the age of twenty-one he wrote a treatise upon the binomial theorem which has had a European vogue. On the strength of it, he won the mathematical chair at one of our smaller universities, and had, to all appearances, a most brilliant career before him. But the man had hereditary tendencies of the most diabolical kind. A criminal strain ran in his blood, which, instead of being modified, was increased and rendered infinitely more dangerous by his extraordinary mental powers. Dark rumours gathered round him in the University town, and eventually he was compelled to resign his chair and come down to London. He is the Napoleon of crime, Watson. He is the organiser of half that is evil and of nearly all that is undetected in this great city... —Holmes, "The Final Problem"

Holmes echoes and expounds this sentiment in The Valley of Fear stating:

But in calling Moriarty a criminal you are uttering libel in the eyes of the law — and there lie the glory and the wonder of it! The greatest schemer of all time, the organizer of every deviltry, the controlling brain of the underworld, a brain which might have made or marred the destiny of nations — that’s the man! But so aloof is he from general suspicion, so immune from criticism, so admirable in his management and self-effacement, that for those very words that you have uttered he could hale you to a court and emerge with your year’s pension as a solatium for his wounded character. Is he not the celebrated author of The Dynamics of an Asteroid, a book which ascends to such rarefied heights of pure mathematics that it is said that there was no man in the scientific press capable of criticizing it? Is this a man to traduce? Foulmouthed doctor and slandered professor — such would be your respective roles! That’s genius, Watson. —Holmes, The Valley of Fear

The "smaller university" involved has been claimed to be one of the colleges that later comprised the University of Leeds. However, in Sherlock Holmes: The Unauthorized Biography, the "smaller university" is said to be Durham University.

Doyle's original motive in creating Moriarty was evidently his intention to kill Holmes off. "The Final Problem" was intended to be exactly what its title says; Doyle sought to sweeten the pill by letting Holmes go in a blaze of glory, having rid the world of a criminal so powerful and dangerous any further task would be trivial in comparison (as Holmes says in the story itself). Moriarty only appeared in one book because, quite simply, having him constantly escape would discredit Holmes, and would be less satisfying.

Eventually, public pressure and financial troubles forced Doyle to bring Holmes back.

A point of interest is that the "high, domed forehead" was seen as the sign of a prodigious intellect during Conan Doyle's time. In giving Moriarty this trait, which had already appeared in both Sherlock Holmes and the detective's brother Mycroft, Doyle may have intended to portray Moriarty as a man having an intellect equal or greater than that of Holmes, and thus the only man capable of defeating him. Moriarty died when he fell off the Reichenbach Falls while Holmes, as revealed in "The Empty House", only faked his death to make the few remaining Moriarty henchmen expose themselves.