This film is all about loneliness. From Harry to his children and grandchildren, the people he meets -- the runaway, the salesman, the hooker. The only real friend Harry has is his cat.
It shows how lonely people meet each other, and are so friendly, and then part.
They have genuine feelings for each other in their transient relationships.
[deleted]
Agree. The film is about the prevalence or universalness of loneliness in life.
He interacts with a ton of people and things -- the cat Hondo, the friend who died, the woman in the apartment who invites him to come to Miami, the black guy, his kids, the hitchhikers, the medicine salesman, the chess players on the park, the Indian in jail, the hooker etc etc.
Yet in the end, noe of those relationships really last; none of them provides any sort of fulfillment. He can't escape loneliness through any of those people or animals.
What really drives the theme of loneliness is that our protagonist is a nice, friendly, sociable, well-dressed old man whom everyone seems to like. That even he has to rely on his cat really shows that loneliness spares no one. Loneliness isn't just for people who don't know how to socialize.