> Writing is an art, not a science.

Writing fiction may be an art, but writing nonfiction is a craft. And essays are nonfiction.

The creator of art seeks somehow to offer fresh insight, often employing some form of novelty, be it technique, medium, context, perspective, etc.

Craft, however, isn't about novelty; it's about engineering a clear convincing message effectively, efficiently, and ideally... memorably and with elan.

I admit the line between art and craft is often blurry (probably because the craftsman has taken too much artistic license). Unlike art, the techniques employed in an essay should never impede its purpose. There, it's only the message that matters, not the medium.