Roald Hoffmann in American Scientist:
Although abstract art has been with us for only about 100 years, sometimes it seems that there are more abstract-art movements than there are scientific “-ologies.” The list begins with cubism, and will not end with postmodern painting. Recognizing that there are degrees of the abstract, my perception of the essence of this artistic direction involves several factors.
First of all, abstraction is oppositional, wanting to be seen as alternative to such ideals as naturalistic representation and the figurative. I will not say “alternative to reality,” for (to paraphrase Magritte) the two-dimensional surface of the most photorealist painting still is not its subject. Not unexpectedly, much theory of the abstract disclaims a definition by opposition. Art desires a broader conception of what stirs the imagination…
To be abstract, chemistry might thus have to be oppositional. But opposed to what?
More here.