Answer: Mathematics

In 1895, per the last will and testament of Alfred Nobel, the largest share of his fortune was set aside to create a foundation encouraging and rewarding innovation and advancement in the sciences and culture. The original categories were Physics, Chemistry, Medicine, Literature, and Peace. Later, in 1968, Sweden’s central bank Sveriges Riksbank established The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, expanding the stable of prize categories to six.

The category that remains curiously missing from the list is Mathematics. Although there has been over a century of speculation as to why Alfred Nobel did not include mathematics, very few of the theories hold water. For years, the rumor was that Nobel had a grudge against a mathematician his wife had an affair with (a rather odd theory given that Nobel never married).

Although Nobel never explained why he selected the categories as he did, a more practical theory on the matter would be that Nobel didn’t find the independent study of mathematics particularly interesting or wasn’t interested in theoretical discoveries and, ever more practically, that there was already a very well established and noteworthy scientific journal in Sweden that covered research in all fields of mathematics (Acta Mathematica, established in 1882).