D O C . 4 8 1 P H Y S I C S A N D T H E E S S E N C E O F T H I N G S 7 6 3 They were replaced by the electromagnetic field, together with the gravitational field. The theory of relativity gave a consistent completion of this theoretical sys- tem, which included Newton’s system as more or less sufficient for many prob- lems: none of his results are lost, but the radius of the phenomena that they can control has grown wider. But the fundamental principles of the theory of these fields do not allow us to have a clear concept of everything that is empirically known. Bohr’s theory of spec- tra and the principles collected under the heading of “quantum theory,” which have perfected our knowledge of the essence of matter and its radiation to such a high degree, do not seem to fall within the theory of these fields.[4] A new theoretical foundation is being formed. This step will also be completed but the conviction is gaining ground that the investigation of real things and phenomena is a process that will never end. Published in La Prensa, 3 May 1925. Transcribed from a low-quality original. [1]Before traveling to South America, Einstein had been asked to write a series of articles on sci- entific topics for La Prensa (see Abs. 539). He visited the newspaper’s offices on 30 March 1925 (see Doc. 455, entry for 30 March 1925). [2]See Einstein 1905j (Vol. 2, Doc. 15). [3]Michael Faraday, James C. Maxwell, and Heinrich Hertz. [4]Einstein earlier expressed himself in similar terms regarding the issues raised by Niels Bohr’s work (see, e.g., Doc. 375).