1926–2013 · American screenwriter & novelist · wrote Star Trek’s “The Enemy Within” (1966)
Richard Burton Matheson was an American novelist and screenwriter in horror, fantasy and science fiction — author of I Am Legend (filmed as The Last Man on Earth) and The Incredible Shrinking Man, and a frequent Twilight Zone writer. He wrote exactly one Star Trek episode, “The Enemy Within” (1966) — the first in which Dr. McCoy pronounces something dead with the four words that became the series’ most-quoted diagnosis. One honest caveat: the shooting script passed through three hands — Matheson’s 2nd Draft, a John D.F. Black polish, then Gene Roddenberry’s Final Draft rewrite of 8 June 1966 — so which typewriter produced those four words is not documented. The on-screen credit reads “Written by Richard Matheson.”