Royce's friendly but longstanding dispute with William James, known as "The Battle of the Absolute," deeply influenced both philosophers' thought. Stanford Encyclopedia of Philosophy
Royce and James had always disagreed deeply concerning the proper understanding of religious phenomena in human life. When James delivered the Gifford Lectures in 1901 and 1902, he directed many arguments against Royce's idealism, though he did not there target his friend by name. James's lectures, published as The Varieties of Religious Experience, were a popular and academic success . Royce believed that James, who had never been regularly affiliated with an established church or religious community, had in that work placed too much emphasis on the extraordinary religious experiences of extraordinary individuals. Royce's first education was into a strongly Protestant world view, he always retained a respect for the conventions of organized Christianity, and his writings exhibit a consistent and deep familiarity with Scripture. He sought a philosophy of religion that could help one understand and explain the phenomena of ordinary religious faith as experienced by communities of ordinary people. There was a deeper difference between them, as well, and it centered on a metaphysical point. Royce's 1883 insight concerning the Absolute was at bottom a religious insight. Contrary to the open-ended pluralism and pragmatism of James, Royce was convinced that the object and source of religious experience was an actual, infinite, and superhuman being. Royce did not attempt to work out his religious philosophy until after James's death, however. In 1911 Royce finally composed the lectures that responded to James. These were published in 1912 as The Sources of Religious Insight. It is here that the theoretical and practical threads of his late thought began to come together. Royce himself said of the Sources: "It contains the whole of me in a brief compass" (Clendenning 1970, 570).