Dr. Hastie Lanyon is a reputable London doctor and, along with Utterson, formerly one of Jekyll’s closest friends. As an embodiment of rationalism, materialism, and skepticism, Lanyon serves a foil (a character whose attitudes or emotions contrast with, and thereby illuminate, those of another character) for Jekyll, who embraces mysticism. His death represents the more general victory of supernaturalism over materialism in Dr. Jekyll and Mr. Hyde.
He serves as a specialist with complete higher medical education, who is constantly engaged in the maintenance or restoration of human health through the prevention, diagnosis, and treatment of diseases and injuries. He was a hearty, healthy, dapper, red-faced gentleman, with a shock of hair prematurely white, and a boisterous and decided manner.
The sincerity of this man may seem to someone as somewhat theatrical, but it was based on a truly sincere feeling. Because there were people who were old friends, who were friends at school and in college, but for Dr. Hastie Lanyon it was a pleasure to see each of them.
The author pays big attention to his relationship with Dr. Henry Jekyll. The attitude is shown in the next letter: “DEAR LANYON, You are one of my oldest friends; and although we may have differed at times on scientific questions, I cannot remember, at least on my side, any break in our affection. There was never a day when, if you had said to me, ‘Jekyll, my life, my honour, my reason, depend upon you,’ I would not have sacrificed my left hand to help you. Lanyon, my life, my honour my reason, are all at your mercy; if you fail me to-night, I am lost. You might suppose, after this preface, that I am going to ask you for something dishonorable to grant. Judge for yourself”.
Dr. Hastie Lanyon in the Essays