People's answer to the question of "What is art?" varies, but for me art is emotional communication. Intellectual communication is not art, merely information. Du Champ's urinal was art originally because it was shocking, but it is not art now because it is no longer shocking, so what art is varies in time with the emotional flow of the observer, and of society.
This also means that art and its meaning is deeply tied to humanity and society, as all emotions step from social interactions, and also of it time, having different meanings and power at different times, and in different societies. The scribbled characters on a receipt may be simple commerce at one time, but in thousands of years, as the last mark of a dead civilisation, may gain new emotional significance and become an artwork. By the same token, a meaningful portrait of a saint or revolutionary leader may, in distant years, fade in feeling to become a mere factual image.
