Just to add another layer of refinement and correction to this
palimpsest, the concept of
mono no aware did not develop in the
Heian Era or begin with the
Tale of Genji, as is so often claimed, but was actually invented from scratch in the
1760s by
Motoori Norinaga, a nationalist scholar of the
kokugaku school who was attempting to distill a native, uniquely Japanese aesthetic that could be distinguished from Chinese cultural tropes.
Norinaga most famously applied his theory of mono no aware to the Tale of Genji, and indeed many textbooks now erroneously date the concept from that time, but Norinaga believed that the concept applied to all Japanese literature all the way back to the Kojiki, boldly making the blanket statement that, "all Japanese poetry
is composed through knowledge of mono no aware."
Norinaga believed that the Japanese as a race had a singular capacity to experience the objective world in a direct fashion, to profoundly understand the objects and the natural world around them without having to resort to the mediation of language. Moreover, not only could the Japanese uniquely understand the world in this direct way, but their language was also uniquely suited to express this direct connection to the world.
On an interesting side note, although mono no aware is often also associated with cherry blossom viewing, there is no evidence that cherry trees were more important than any other trees in the Heian Era, and indeed, the Yoshino cherry tree that is so ubiquitous in modern Japan was not even invented by horticulturalists until the 1820s, more than 20 years after Norinaga's death. Before that, Japanese cherry trees could only be found high in the mountains, didn't have many blossoms, and viewing them required a special trip that only the wealthy could afford.