What is the theme in The Snow Leopard by Peter Matthiessen?

Buddism is a major theme in this book. Matthiessen and his wife Deborah were devout Zen Buddhists. Zen Buddhism is a ancient religion dating back to the 7th century in China. A great deal of the doctrine is ascribed to the teachings of Siddhartha Gautama an ancient, holy mendicant who became the Buddha.