Why do a Chinese brush painting is meant to not be "corrected ” if a mistake was made in the artwork ?

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Explanation:The aim of the traditional Chinese painter was to capture not only the outer appearance of a subject but its inner spirit as well. This meant that the artist had to understand something more than just how the subject was created--they had to think about the subject's essence.  Because of this, Chinese ink wash painting may be thought of as an art of expression that captures the unseen as much as the seen.

To accomplish his goal, the Chinese painter usually rejected the use of color because he thought that color was a distraction. He also rejected the Western use of light and shadow as a means of modeling ("modeling" makes the object seem more three-dimensional), along with opaque pigments (paint that is not see-through or transparent) to conceal mistakes. Instead, the artist relied on line—the characteristic line of the inked brush.  

In Chinese brush painting, no sketch is prepared and no model is used; the artist paints with rapid strokes, transferring what he sees in his mind directly to the paper. There are no corrections: from first to last stroke, the artist must 'get it right.'   This, again, is different from Western watercolor technique, where corrections and overpainting are a part of the process.  The discipline that this kind of mastery requires derives from the practice of calligraphy.

The Chinese believed that simple beauty, harmony, serenity and tranquility could be discovered in a symbol (such as in calligraphy), or in a bird, plant or animal.  Remember that Chinese Brush Painting is meant to be more than a representation of an object; it is also a symbolic expression. This is why a full plant is never painted, but rather a few blossoms or branches which will represent the plant in it's entirety.  Because the artist does not look at the subject as he paints, he believed he was bringing it forth from his mind and heart and becoming part of nature in the process.