It looks like we're really talking about two letters -- the one you have a photocopy of, above, and the one the New York Times (also known as "the newspaper of record") vetted and printed in 1972. There's no reason at all why Prof. Einstein, if he liked the first two sentences of a letter he'd written to one person, couldn't just go ahead and repeat those two lines when writing to someone else. According to the New York Times, the letter they printed a passage from was written to a Rabbi, who had written to Einstein when he found himself unable to console his nineteen-year-old daughter over the death of her sixteen-year-old sister. It seems clear that these two quotes come from two different letters. It's great that you were able to identify the specific source of one of them. It would be great if someone could find as detailed information about the other!
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