We are the pencil, writing, drawing, living our way through life. We plan our paths and where we will head, but not everything works out. We have drawbacks, we make mistakes, and we need to start over. That's when the eraser comes in handy.
The invention of the eraser makes it so whenever we make mistakes, which is quite often if you are an average human being, things can be redone. If everybody wrote with pens, there would be ink scratches on stories and poems and artists would have to redo their artwork until it turned out right. There would be an undeniable source of needed perfection, right there in that pen. But pencils, topped with an eraser, allow us to make mistakes - this doesn't mean that we make them throughout every word we write or every line we draw, or that they are supported in any way - it gives anyone the liberty to start over again.
The eraser is important because it allows school children and other people to make notes in pencil, even if they make mistakes. The eraser also allows people to make beautiful pencil drawings and to correct errors. Figuratively, the concept of an eraser inspires people. It is the idea that mistakes are not permanent and that people can start over again.
WIthout the eraser, it was a lot harder to change something you had written down or drawn. Beyond the revolutionary change for writers, the eraser revolutionized the works of art that artist could create. It allowed for better detail in graphite design and helped to increase the amount of shading.
The eraser is an essential invention because it enhances the tools of writers and artists to give them more freedom. Because of the eraser, the markings made by writers and artists with pens and pencils are not permanent, as they they can be erased with an eraser and the work can be recreated. The eraser gives writers and artists the freedom to make mistakes, change their minds, and, in turn, make better creations.
Erasers as we know them today are a relatively modern invention. But erasers as a general category are age-old. The ancient Greeks and Romans relied on palimpsests and smoothable wax tablets to ensure erasability. Those gave way, eventually, to White-Out and Photoshop's "magic eraser" tool and, of course, the ultimate undoer of deeds: the delete key. But erasers are far from obsolescence -- just as writing itself is far from obsolescence.
The eraser gives a writer the ability to create mistakes with no expense. An outlet for mistakes to become normalized would lead to a slippery slope in many disciplines, leading to experiments with illogical conclusions that tried to follow the confusing trials of fixed mistakes through time. To take this claim a step further, the eraser actually hinders humanity from perfection. If one can only take a math test in a black sharpie, the individual would thoroughly study to understand the material, thus possibly rising test scores and the pursuits of perfection.
Practice makes perfect. Practice would include committing to the trial until a mistake occurs. Once the mistake occurs, the trial is terminated. This meticulous practice technique would surely create more observed and precise students and scientists.
For artistry, an eraser is an avenue for unnatural forms. I would debate true artistry comes from inherent creativity, and a perceived flaw is actually an outlet for further artistic expression. Art cannot create objective perfection, only subjective. If subjective events yield undesirable circumstances, the artist would truly become more creative if the "mistake" is permanent.