The resonance of the artist's inner content with his time is what will generate the form of his art work. In other words the art form is somehow generated automatically when the artist's ideas are in sink with what's going on in his time, thus the necessary precedence of the content of the art work, the content is indeed the essence of the art work.
In this lies the fundamental difference between the modern approach of the visual arts with the realism of Renaissance and post-Renaissance times. In religious times and early modern times form had to bend to the reality2 projected onto all members of society by its "men of power". Form was assumed to project the subject of a work, it was thus a kind of photocopy of the "no-brainer" first degree image reflected upon the observer's retina.
Twentieth century artists rejected this assumption on the ground that science indicated that reality was a lot larger then what the eye was physically able to see and consequentially they tried to define a new approach more in sink with the impact of science and technology on their times.
Alas, in late modern times marketization favored form over content. Free form was indeed less disturbing for the art establishment than free content. But, in finale, the market has to assume the full responsibility for the dismissal of the essence of art works from "market-successful" artistic creations in late modernity.
The total confusion wherein the art world has been plunged is indeed a direct result of this dismissal of the essence of art from the works that the market retained.
I'm not speaking here of this idea of the sacred in art that follows the renaissance, I'm speaking about the universality of art's societal functionality, I mean the creation by artists of visual signs about the worldview of the men of knowledge in their time.
In the past religious times and early modern times the first degree image projecting on the retina was the imposed form to illustrate the imposed content of visual arts. Artists toiled to reproduce first degree images as illustrations of the stories of the men of knowledge of their times, religious stories in religious times and the stories about individualism and private property in early modern times.
The artist was firmly discouraged to let lose his intellect.
Today, it is assumed that each and everyone should make the best use of his intellect, is this not so?
But visual artists struggled to reconcile the use of their intellect with the first degree image on their retina. This fast appeared to be an impossible task for the intellect can't be constrained by such a narrow perception as the first degree image on the retina. The intellect has to be let loose in order for it to flourish.
But then how to let the intellect derive a visual form out of its activity?
Artists struggled with this particular question during all of the twentieth century and the question has still not found an accepted answer.
1. Wassily Kandinsky. "on the problem of form" 1912. In Herschel B. Chipp. Theories of modern art. University of California Press.
2. The reality projected onto all was, until recently, the knowledge of the "men of knowledge" of the day that was imposed on all through the power at the hands of the "men of power" of the same day.