alt Hacker NewsOne of the most famous mathematicians of all time studied number theory. He wrote an apology to humanity for all of the very smart and capable people wasting time studying number theory, since these things are clearly unless old puzzles with no practical use whatsoever. Now, 100 years later, these results underpin all of modern public key cryptography.
And then there's G. H. Hardy, famous number theorist, who wrote an "Apology" for mathematics in the sense of defending the study of number theory for its own sake because it's beautiful.
Which one were you referring to?