According to author William Anderson, Muir exemplified "the archetype of our oneness with the earth",[10] while biographer Donald Worster says he believed his mission was "saving the American soul from total surrender to materialism".

[12] In his autobiography, he described his boyhood pursuits, which included fighting, either by re-enacting romantic battles from the Wars of Scottish Independence or just wrestling on the playground, and hunting for birds' nests (ostensibly to one-up his fellows as they compared notes on who knew where the most were located).

He held a strong connection with his birthplace and Scottish identity throughout his life and was frequently heard talking about his childhood spent amid the East Lothian countryside.

[16] Stephen Fox recounts that Muir's father found the Church of Scotland insufficiently strict in faith and practice, leading to their immigration and joining a congregation of the Campbellite Restoration Movement, called the Disciples of Christ.

[11]: 76  Muir took an eclectic approach to his studies, attending classes for two years but never being listed higher than a first-year student due to his unusual selection of courses.

Muir left school and travelled to the same region in 1864, and spent the spring, summer, and fall exploring the woods and swamps, and collecting plants around the southern reaches of Lake Huron's Georgian Bay.

With his money running low and winter coming, he reunited with his brother Daniel near Meaford, Ontario, who persuaded him to work with him at the sawmill and rake factory of William Trout and Charles Jay.

Muir built a small cabin along Yosemite Creek,[29]: 207  designing it so that a section of the stream flowed through a corner of the room so he could enjoy the sound of running water.

[25]: 172 During these years in Yosemite, Muir was unmarried, often unemployed, with no prospects for a career, and had "periods of anguish", writes naturalist author John Tallmadge.

This notion was in strong contradiction to the accepted contemporary theory, promulgated by Josiah Whitney (head of the California Geological Survey), which attributed the formation of the valley to a catastrophic earthquake.

But Louis Agassiz, the premier geologist of the day, saw merit in Muir's ideas and lauded him as "the first man I have ever found who has any adequate conception of glacial action".

[39] Muir, Mr. Young (Fort Wrangell missionary) and a group of Native American Guides first traveled to Alaska in 1879 and were the first Euro-Americans[40] to explore Glacier Bay.

In June 1889, the influential associate editor of The Century magazine, Robert Underwood Johnson, camped with Muir in Tuolumne Meadows and saw firsthand the damage a large flock of sheep had done to the grassland.

On September 30, 1890, the US Congress passed a bill that essentially followed recommendations that Muir had suggested in two Century articles, "The Treasures of the Yosemite" and "Features of the Proposed National Park", both published in 1890.

In early 1892, Professor Henry Senger, a philologist at the University of California, Berkeley, contacted Muir with the idea of forming a local 'alpine club' for mountain lovers.

[4]: 107–108 [46] The Sierra Club immediately opposed efforts to reduce Yosemite National Park by half, and began holding educational and scientific meetings.

[47] In 1899, Muir accompanied railroad executive E. H. Harriman and esteemed scientists on the famous exploratory voyage along the Alaska coast aboard the luxuriously refitted 250-foot (76 m) steamer, the George W. Elder.

According to Muir biographer Bonnie Johanna Gisel, the Carrs recognized his "pure mind, unsophisticated nature, inherent curiosity, scholarly acumen, and independent thought".

According to Williams, in nature, especially in the wilderness, Muir was able to study the plants and animals in an environment that he believed "came straight from the hand of God, uncorrupted by civilization and domestication".

Historian Catherine Albanese stated that in one of his letters, "Muir's eucharist made Thoreau's feast on wood-chuck and huckleberry seem almost anemic".

This would become a constant theme in Muir's writings, as he attacked the dominant white culture's destructive and greedy ways, and its anthrosupremacist mindset that placed humans above all else and recognized no intrinsic value in ecosystems or wildlife species beyond whatever profit could be gained by exploiting them.

Describing the sight of two African Americans at a campfire, he wrote, "I could see their ivory gleaming from the great lips, and their smooth cheeks flashing off light as if made of glass.

[73]Some of Muir's associates cited by Brune and others, such as Joseph LeConte, David Starr Jordan, and Henry Fairfield Osborn were closely related to the early eugenics movement in the United States.

[72] Aaron Mair, who in 2015 became the first Black president of the Sierra Club board, stated that the contents and framing of Muir in Brune's post "are a misrepresentation".

Mair went on to state that Brune, "did not consult him or the other two Black board members before pushing ahead on what he called a “revisionist” and “ahistorical” account of Muir's writings, thoughts and life.

God does not appear, and flow out, only from narrow chinks and round bored wells here and there in favored races and places.”[72]With population growth continuing in San Francisco, political pressure increased to dam the Tuolumne River for use as a water reservoir.

"As a dreamer and activist, his eloquent words changed the way Americans saw their mountains, forests, seashores, and deserts", said nature writer Gretel Ehrlich.

[84] He not only led the efforts to protect forest areas and have some designated as national parks, but his writings presented "human culture and wild nature as one of humility and respect for all life".

[25] The primary aim of Muir's nature philosophy, writes Wilkins, was to challenge mankind's "enormous conceit", and in so doing, he moved beyond the Transcendentalism of Emerson to a "biocentric perspective on the world".

[54] In the opinion of Enos Mills, a contemporary who established Rocky Mountain National Park, Muir's writings were "likely to be the most influential force in this century".