There’s a popular but erroneous idea circulating today that Christianity is indifferent to—and perhaps even the inherent enemy of—environmentalism. In fact, important Christian thinkers and leaders of the past have encouraged deep respect for nature. One monumental example is John Muir, virtual patron saint of the National Parks system and founder of the Sierra Club. Muir was reared in the Stone-Campbell movement. His father brought the family to the U.S. because of the Campbells’ preaching, when John was ten years old.

John himself became an active disciple, teaching Sunday school, memorizing the New Testament and large parts of the Old. That biblical underpinning remained with him the rest of his life, informing his diction, imagery, and ideas when he wrote about nature.

Muir’s faith affected his understanding of nature. He believed nature was the “name for an effect whose cause is God.” Flowers, he said, offer “glorious traces of the thoughts of God, and leading on and on into the infinite cosmos.” In his journal, My First Summer in the Sierra, he reports seeing the evidence of God in the magnificent mountains of California:

The radiance in some places is so great as to be fairly dazzling, keen lance rays of every color flashing, sparkling in glorious abundance, joining the plants in their fine, brave beauty-work—every crystal, every flower a window opening into heaven, a mirror reflecting the Creator.

Muir was heir to a venerable Christian tradition that taught that God wrote two books, not just one: the Bible and “the book of nature.” Growing up in Scotland, John had absorbed the truth of nature’s revelatory power from personal observation and his father’s example. One day his father called the family outside to revel in the splendor of the Scottish countryside: “Come, mother! Come, bairns! And see the glory of God. Hush and wonder and adore, for surely this is the clothing of the Lord Himself.” “Everything” in nature, John wrote years later, “is perfectly clean and pure and full of divine lessons.”

Christians today should remember and be grateful for this largely self-taught genius, who declared that the landscapes on his way to church were “fraught with the glory of the creator.” Muir testifies to the religious roots of the American environmental movement, and he challenges Christians today: If you truly love the Bible, you must also love, respect, and care for God’s other masterpiece, the book of creation.