In Ralph Waldo Emerson's Nature, what does he mean by the line, "The sun illuminates only the eye of the man, but shines into the eye and heart of...

Emerson feels that, as
we age, we gradually begin to truly see less and less. It is not the case
that we cannot physically see what is around us, we simply lose sight of what things are really
important; we may get caught up in materialism, our jobs, or our other responsibilities. He
says,

To speak truly, few adult persons can see nature.
Most persons do not see the sun. At least they have a very superficial seeing. The sun
illuminates only the eye of the man, but shines into the eye and the heart of the child. The
lover of nature is he whose inward and outward senses are still truly adjusted to each other;
who has retained the spirit of infancy even into the era of manhood.

Thus, when we become adults, we forget to stop and smell the roses,
to use a common expression. The sun is there and while we see it with our
eyes , we fail to see it with our hearts. The child, who has not yet
learned to ignore and forget, is still affected by nature in the way we are meant to be; nature
is God's direct...