Symbolism, Imagery, Allegory
Toward the end of the book, Primo describes an execution: a man is hanged for having taken part in a rebellion among some prisoners in Birkenau, the adjoining death camp. Notice how this man's last words overshadow those of the SS Officer:
Who answered 'Jawohl?' Everybody and nobody; it was as if our cursed resignation took body by itself, as if it turned into a collective voice above our heads. But everyone heard the cry of the doomed man, it pierced through the old thick barriers of inertia and submissiveness, it struck the living core of man in each of us:
'Kamaraden, ich bin der Letzte!' (Comrades, I am the last one!') (16.19-20)
Why is this event so important and powerful to Primo? Well, the prisoners would usually unhesitatingly obey any SS officer asking them a question. Here do that only in a halfhearted manner. Instead, their focus is on the man about to be hanged—the "last one." He cuts through their apathy, and gets right to the inner "man" in each of them. This ability to be a "man" (a human as opposed to a broken-down shell) is something Primo has continually mourned as being lost. Here, it briefly comes back.
This unnamed man, this "last one," symbolizes the strength and willpower—the inner human essence—that has been so methodically and brutally taken away from the rest of the prisoners. He's a symbol of "the living core of man."