Of course that is assuming that Dowd is insane. At the end of the film it is implied that Harvey is real. Jimmy Stewart never acted better than in this gentle comedy.
Bonus:
Insanity Never Looked Sweeter
- Donald R. McClarey
Donald R. McClarey
Cradle Catholic. Active in the pro-life movement since 1973. Father of three, one in Heaven, and happily married for 43 years. Small town lawyer and amateur historian. Former president of the board of directors of the local crisis pregnancy center for a decade.
This bio pic of Jimmy Stewart looks good.
https://www.youtube.com/watch?v=EURriesRel0
The psychiatric nurse was played by Peggy Dow, who apparently still alive at age 98.