Most physicists have no difficulty in seeing physics as a single subject. Yet this view, which was straightforwardly tenable until the end of the nineteenth century, is radically inconsistent with the situation since then. There has been a divorce between the theories of the very small and the large scale. Amongst those worried about this the response has been to search for a ‘theory of everything’. This phrase has many closely related connotations and to determine which, if any, is the correct one is an inspiring and useful task, not least for the unexpected by-products. So far, however, it has proved a task without any successful outcome. In this book I draw attention to an alternative. Unnoticed by many today, Eddington in the 1930s made great strides towards a different solution of the enigma.

It is half a century since I first succumbed to the Eddingtonian magic – I paraphrase Thomas Mann's phrase to try to do justice to my youthful if uncritical absorption in Relativity Theory of Protons and Electrons, which Eddington had published five years or so earlier, in 1936. I had already enjoyed his authoritative Mathematical Theory of Relativity with no more difficulty than that produced by the complex mathematical techniques which were new to me. Looking back on it, it surprises me that I could take in without a qualm so many of the unorthodox philosophical views in that book. But Relativity Theory of Protons and Electrons was a different matter. Another clutch of mathematical techniques was not enough to obscure a radically new position.