I assumed OP was using a different definition of art (https://en.wiktionary.org/wiki/art#Noun):

> 2. (countable) Skillful creative activity, usually with an aesthetic focus.

> She's mastered the art of programming.

..

> 7. (countable) Skill that is attained by study, practice, or observation.

If that doesn't convince you, compare with such phrases as "The Art of War", "artisan bread", or "liberal arts" (which includes topics like philosophy).