In the beginning of Night, Eliezer’s identity is that of an innocent child, a student of Talmud, and a devout Jew. But the concentration camps experience strips him (and his fellow Jewish prisoners) of his identity. Eliezer’s hair is shaved, he’s dressed like all of the other prisoners, and in facing the atrocities of the camp, he loses his innocence (he’s no longer a child) and his faith in God (he’s no longer a devout Jew or student of Talmud). Eliezer and all of the other prisoners are given numbers instead of names. They are no longer individuals, but prisoners, "creatures," and eventually simply bodies. The longer they remain in camps, the more they are reduced to a mere physical presence, losing themselves to their self-preservation instinct, and eventually becoming simply hungry, nearly dead bodies. They are denied a spirit, a soul, human dignity, and even their bodies are denied the sustenance needed to survive – food, water, adequate shelter, and sleep.
Even though Eliezer is not immune to the degradation of his spirit, he manages to cling to his personhood through his connection with his father.