"The Bet" tests the convictions of a lawyer who claims that any kind of life is better than no life at all by subjecting him to fifteen years of subhuman existence, trapped in a house with nothing but books for company. Although physically comfortable, the lawyer is deprived of one of the standard markers of being human—being part of a community of other humans. As time goes by, the lawyer is slowly driven to reject the rest of his human existence as well. When he forfeits victory in the bet for a life of spirituality or perhaps even suicide, the story seems to point to the idea that without interaction with others, our humanity cannot survive.
The story ends up showing that the quest for knowledge has a damaging effect on living life.
The story ends up showing that the only way to get to the true essence of life is to toss out every other aspect of existence. The tragedy is that this is obviously a totally unworkable route for most.