In "The Secret Sharer" by Joseph Conrad, a character observes "Meaning depends upon sharing"; another says "Happiness was born a twin." Both of these observations dispute the young man's original viewpoint that spending fifteen years in solitary confinement is worth the two million dollar bet. While the young man at first reads to occupy his time, later
[H]is reading suggested a man swimming in the sea among the wreckage of his ship, and trying to save his life by greedily clutching first at one spar and then at another.
The lawyer seeks to find some communion with the thoughts of other men, but his act of reading cannot substitute for human companionship. There is in man the need to love and be loved, and without it he is not a man.
The lawyer has no one by whom to measure himself. He plays the piano, but there is no one to enjoy the music but himself and he gives no joy to anyone. He reads the thoughts of others, but has no one with whom to exchange them. Consequently, his psychological condition deteriorates as he has no other opinions and emotional reactions against which to balance himself. This is why the young man writes in his letter before he escapes that he "once dreamed [of the money] as of paradise and which now I despise."
In summation, here are 3 reasons:
- There is no significance to one's life if it is not shared with others. A person cannot remain happy unless he has someone to share this happiness, and other emotions, as well.
- People need other people: "No man is an island unto himself," John Donne wrote. It has been proven that human babies will die without love and affection and physical human contact.
- People's psychological state deteriorates in solitude because they need others against whom to measure themselves. Cultures develop as people perform certain rituals and customs, eat and drink certain things, etc. There is a security that comes with belonging to a culture. Alone a person becomes estranged from the world and often is haunted by self-doubt and thoughts that can become delusional.