Were I called on to define, very briefly, the term Art, I should call it 'the reproduction of what the Senses perceive in Nature through the veil of the soul.' The mere imitation, however accurate, of what is in Nature, entitles no man to the sacred name of 'Artist.'

This quote is saying that in order to be an artist, one must not just copy what they see in nature. Instead, they must try to capture the impressions of nature, understanding the feeling and soul behind it. To do this, the artist must take what they experience through their senses and use their own creativity and imagination as a “veil” to interpret it. This allows them to create a work of art that is often much more creative and thought provoking than a simple imitation of reality.