Philosopher and psychologist Ken Wilber is devoted to the study of what he calls "integral" understanding—exploring the common threads of the world's cultures. He is the author of many books, including "The Spectrum of Consciousness," "No Boundary," "Up from Eden," "Sex, Ecology, Spirituality," and "A Brief History of Everything." He lives in Denver, Colorado, where he works with the Integral Institute, a think tank he founded that encourages the cross-fertilization of ideas, and moderates the website Integral Naked.

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