The search for a unity of nature is the focus of Einstein's scientific biography. In the last three decades of his life he attempts to reach this goal by creating a unified theory of gravitation and electromagnetism.

Again and again he formulates new approaches to such a theory, and again and again he fails. Nevertheless, the methods and insights he achieves turn out be productive, even though at first primarily in the field of mathematics.

Einstein's research is stimulated by, among others, Hilbert and Weyl.