Though scholars may continue to disagree about who most deserves the credit or the blame for popularizing the idea of historical incommensurability, at least one thing seems certain: if this idea is right, then analogical reasoning in history becomes an impossibility. If I sincerely believe that a given event in the past belongs not just to a foreign country but to a world so different from my own as to break all ties of communication between them, then I have no license to speak about the past at all. If I am bound by the rules of my own time, then the past and all its events become in effect unknowable. A past that is utterly different is more than merely past; it has no claim on my knowledge and it might as well blink out of existence altogether. This is more than merely a matter of logic; it has political consequences. If every crime is unique and the moral imagination is forbidden from comparison, then the injunction “Never Again” itself loses its meaning, since nothing can ever happen “again.”
Source : Why Historical Analogy Matters
