Composition

Everybody immediately responds to subject matter in art. 

A picture of a butterfly and a picture of a snake do not get the same response.
In addition to subject matter*, the formal aspects of visual composition are like the grammar of a language. In writing, a story is written with words - subject matter. Like good literature and good poetry is more than words and subject matter, art is more than pictures. The organization, the sentence structure, the style, and so on can make or break a good story. In art, the way the formal elements are arranged can make or break a good picture idea.
 

The use of design principles applied to the visual elements is like visual grammar. When children learn art, it is like learning to read and write the language of vision. When they develop a style of expressing visual ideas, it helps them become visual poets. Looking for the visual effects of design principles does not have to limit an artist's options. It can focus an artist's experimentation and choice making.