Title to the contrary, this is better on Muir in his time than in ours. Turner does an admirable job of tracing the life of America's best-known naturalist. But he doesn't even try to explain why the white-bearded sage (remembered most for his five-year saunter in Yosemite and his struggle to preserve the area as a national park) is the only naturalist-explorer who even comes close in American lore to the likes of Boone and DeSoto, who of course had much different ideas about what should be done with the vast wildernesses of the New World. According to Turner, Muir's habit of long rambles through the landscape--first the broad folds of the Scottish Lammermuirs, later California's rugged Sierra, frozen Alaska and wild places around the world--became psychological and spiritual escapes from the thrashings of his severely disciplined boyhood in Scotland, his father's religious zealotry, the confining regimen of a Wisconsin frontier from, and the deadening routines of civilized life. Muir was a man both of his time and before his time. His thinking was influenced mostly by the Bible but increasingly by the Romantic poets in Europe, by Emerson and other American transcendentalists, as well as by the new breed of earth scientist who claimed the history of the planet could be explained by ongoing forces, not a divinely wrought or even natural catastrophe. Muir came to reject the Calvinist belief that the world was made expressly for man, writing that the universe would be ""incomplete without the smallest transmicroscopic creature that dwells beyond our conceitful eyes""--a belief that ultimately became the bedrock of the modern environmental movement. The kind of anti-people, anti-city bias apparent in this and much else of Muir's writing, often excused as some Scottish-Calvinist quirk, has also tinged the American conservation movement--another fascinating subject Turner fails to explore in an otherwise noteworthy biography.