How is naturalism reflected in "a man said to the universe"?

Naturalism is defined as philosophical view where it is believed that everything that exists in the universe is just physical matter thus supernaturals do not exist. The poem is a very concise expression of a naturalist desire of recognition of existence. However, everything seems to be indifferent to his existence. It is reflected in the poem that no one higher being is obligated for our existence, certainly a naturalist view.