Alfred North Whitehead, one of the twentieth century's most original metaphysicians and a major figure in mathematical logic. In “Enquiry Concerning the Principles of Natural Knowledge”, published in 1919, he introduced the method of extensive abstraction, performing the alternative of the Albert Einstein’s theory of relativity. It did not attract much attention of professional physics on account of its abstractness and complexity. His works include The Organisation of Thought (1916), The Concept of Nature (1920), The Principle of Relativity (1922), Science and the Modern World (1925), Religion in the Making (1926), Symbolism (1927), The Aims of Education and Other Essays (1929), Process and Reality (1929), Adventures of Ideas (1933), and Essays in Science and Philosophy (1947).