The relativity and quantum theories, the theoretical foundation ofmodern physics, are generally held to be abstract systems of ideas,inaccessible to the layman, which no longer show much evidence oftheir human origin. It is, however, the human aspect of the developingscience, more than anything else, which this correspondencebetween Albert Einstein and Max Born renders intelligible.Einstein and Born were both in the front rank of those who contributedtowards the formation of modern physics. In the year 1916, atthe beginning of the correspondence, Einstein had just completedhis papers about the general theory of relativity, and was concentratinghis efforts on the then still very puzzling quantumphenomena. During the years which followed Born, together withhis pupils in Gottingen, took a number of decisive steps which ledto an understanding of these very phenomena. Nothing demonstratesmore clearly the exceptional difficulties which stood in the way of aclearer understanding of atomic phenomena - in spite of the considerableamount of experimental data already obtained - than thefact that these two scientists, who on the human level were on suchintimate terms, failed to agree about the final interpretation of thequantum theory.But their correspondence does not merely bear witness to thedramatic argument about the correct interpretation of atomicphenomena. It also shows the way in which human, political andideological problems are intermingled in this discussion, and for thisreason the contemporary history of the years 1916 to 1954 plays animportant part in these letters. [from Heisenberg's Preface]