in Thoreau’s Journal: 

Nature has looked uncommonly bare & dry to me for a day or two. With our senses applied to the surrounding world we are reading our own physical & corresponding moral revolutions. Nature was so shallow all at once I did not know what had attracted me all my life. I was therefore encouraged when going through a field this evening, I was unexpectedly struck with the beauty of an apple tree –– the perception of beauty is a moral test….