Nature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe. “Nature” refers to the phenomena of the physical world, and also to life in general.
“No matter what people say; we painters work better in the country, everything there speaks more clearly, everything holds firm, everything explains itself... “ - Vincent VanGogh letter to his sister Willemien from Saint-Rémy-de-Provence, 20 January 1890 :
In the desert
I saw a creature, naked, bestial,
who, squatting upon the ground,
Held his heart in his hands,
And ate of it.
I said, "Is it good, friend?"
"It is bitter -- bitter," he answered;
"But I like it
Because it is bitter,
And because it is my heart."