For all cultures, the first true art form is architecture. For Western culture, the upward-reaching cathedrals of the Middle Ages were inspired by the forests of Northern Europe.
The prime symbol of Western culture is the perception of infinite space — a yearning to reach out of the darkness of the trees to the light beyond.
Architecture is the most immediate expression of a culture's "world-feeling," and all other art forms then spring out from it.
Notice how sculptures of saints were originally attached to the churches, but later stepped out of the architecture to stand on their own feet.
Likewise, fresco paintings became detached from the walls as standalone oil paintings, and even classical music came from Gregorian chant, for which the cathedral was designed to carry and amplify.
Even western drama came from religious ceremonies (Spengler talks about how western drama is confessional in nature).
Spengler says this is because all art forms (and all non-natural expressions of life) originate from religion. They may separate themselves physically from the church over time, but are still fundamentally tied to that metaphysical expression.
You cannot define individual art forms because they all blend into each other. Sculpture, painting, and music are merely words, and they are nothing without the prime urge that created them. This is why to define what art is you have to extract the cultural form, or the "inner form-language".
The artists of the present (in the Western culture) aren't really engaged in "art" at all, but merely a kind of craftsmanship. Today’s art lacks the spontaneity and necessity of the word-feeling that birthed the culture’s artistic expression, and this is a natural evolution of all civilizations:
"Of great painting or great music there can no longer be, for Western people, any question. Their architectural possibilities have been exhausted these hundred years. Only extensive possibilities are left to them."
