7 3 0 D O C . 4 3 8 T O S P A N I S H A C A D E M Y O F S C I E N C E S demonstrate how deliberately and affectionately you have studied my life’s work, echoing the poet’s words: “We wish to receive less praise and, instead, may we be read industriously.” You also touched upon the weak point of the theory of light quanta, an arduous subject for our generation of physicists. I believe that those dif- ficulties can only be overcome by a theory that not only fundamentally modifies the principle of energy, but perhaps also expands that of causality. Just a while ago, Tetrode has pointed precisely to such possibilities. Even though the princi- ples for the solution to this basic problem have not yet become clear, nevertheless the new impetus towards the unification of all the forces of nature, born in the cra- dle of the theory of relativity, promises satisfactory results. The method employed in this venture is purely mathematico-speculative, characteristic of Levi-Civita, Weyl, Eddington. In this way one can completely relieve the foundation of phys- ics from the disturbing dualism summed up by those two words, gravitation and electricity. I have found the words you have spoken very significant—a reflection of your optimistic hope in the development of science in Spain. Moments of active partic- ipation in the global progress of understanding depend upon external conditions that have now been realized in your country. I believe that a tormented and imper- iled Europe can turn its eyes full of hope towards this people, which is now heading down the road to scientific work after having produced such grand things in the arts for humanity. Published in Discursos pronunciados en la sesión solemne que se dignó presidir S. M. el Rey el día 4 de marzo de 1923 celebrada para hacer entrega del diploma de académico corresponsal al profesor Albert Einstein. Real Academia de Ciencias Exactas, Físicas y Naturales. Madrid: Talleres Poligráf- icos, 1923, pp. 19–20. A transcript with minor variations appeared in El Debate, 6 March 1923. King Alfonso XIII. Blas Cabrera summarized Einstein’s achievements in his introductory presentation (Discursos, pp. 7–15). On p. 12, Cabrera mentioned phenomena supporting the wave and the corpuscular character of light and the problem of how to reconcile them. For his appreciation of Tetrode 1922, see Doc. 329. Tullio Levi-Civita, Hermann Weyl, and Arthur Stanley Eddington.