He must live by his own light, and let earth live by hers. The forces of nature are to be in this respect his teachers—
But with joy the stars perform their shining,
And the sea its long moon-silvered roll;
For self-poised they live, nor pine with noting
All the fever of some differing soul.
But, though he is to learn from Nature and love Nature and enjoy Nature, he is to remember that she
never was the friend of one,
Nor promised love she could not give;
and so he is not to expect too much from her, or demand impossible boons. Still less is he to be content with feeling himself "in harmony" with her; for
Man covets all which Nature has, but more.
That "more" is Conscience and the Moral Sense.
Man must begin, know this, where Nature ends;
Nature and man can never be fast friends.
And this brings us to the idea of Duty as set forth in his poems, and Duty resolves itself into three main elements: Truth—Work—Love. Truth comes first. Man's prime duty is to know things as they are. Truth can only be attained by light, and light he must cultivate, he must worship. Arnold's highest praise for a lost friend is that he was "a child of light"; that he had "truth without alloy,"
And joy in light, and power to spread the joy.