What causes Jose to stop believing in God?

After failing to obtain a daguerrotype of God, he throws himself into the quest of putting everything on a pendulum. This final quest exhausts him mentally and psychologically. After seeing the ghost of Prudencio Aguilarand communing with the dead, he goes into a rage, destroying the laboratory and attempting to set fire to the house. It takes twenty men to restrain him, which they can only do by lashing him to a tree. Ursula builds a shelter to protect him from the sun and the rain and he remains there.

The final image of Chapter Four‹a humbled and defeated Jose Arcadio Buendia, lashed to a tree‹is a crucial one. Continuing with the Biblical overtones of the book, this tree is meant to suggest the Tree of Knowledge, the tree that was forbidden to Adam and Eve and caused their expulsion from the Garden of Eden. Like them, Jose Arcadio Buendia has overstepped humanity's boundaries with his obsessive quest for knowledge. And like them, his family and his village will be turned out of the Garden, forced to weather plagues (like the insomnia plague) and violence (the magistrate's appearance is a comical foreshadowing of the government "interventions" to come). This novel is as much about humanity's failure to communicate with one another and care for one another as it is about the Buendias.