**Arthur Stanley Eddington**, M.A., M.Sc., F.R.S., Plumian Professor of Astronomy and Experimental Philosophy, University of Cambridge, wrote

*The Mathematical Theory of Relativity*which was published by Cambridge University Press in 1923. We present below an extract from the Preface.

The Mathematical Theory of Relativity

by**A S Eddington**

**Preface**

A first draft of this book was published in 1921 as a mathematical supplement to the French Edition of *Space, Time and Gravitation.* During the ensuing eighteen months I have pursued my intention of developing it into a more systematic and comprehensive treatise on the mathematical theory of Relativity. The matter has been rewritten, the sequence of the argument rearranged in many places, and numerous additions made throughout; so that the work is now expanded to three times its former size. It is hoped that, as now enlarged, it may meet the needs of those who wish to enter fully into these problems of reconstruction of theoretical physics.

The reader is expected to have a general acquaintance with the less technical discussion of the theory given in *Space, Time and Gravitation,* although there is not often occasion to make direct reference to it. But it is eminently desirable to- have a general grasp of the revolution of thought associated with the theory of Relativity before approaching it along the narrow lines of strict mathematical deduction. In the former work we explained how the older conceptions of physics had become untenable, and traced the gradual ascent to the ideas which must supplant them. Here our task is to formulate mathematically this new conception of the world and to follow out the consequences to the fullest extent.

The present widespread interest in the theory arose from the verification of certain minute deviations from Newtonian laws. To those who are still hesitating and reluctant to leave the old faith, these deviations will remain the chief centre of interest; but for those who have caught the spirit of the new ideas the observational predictions form only a minor part of the subject. It is claimed for the theory that it leads to an understanding of the world of physics clearer and more penetrating than that previously attained, and it has been my aim to develop the theory in a form which throws most light on the origin and significance of the great laws of physics.

It is hoped that difficulties which are merely analytical have been minimised by giving rather fully the intermediate steps in all the proofs with abundant cross-references to the auxiliary formulae used.

...

A selected list of original papers on the subject is given in the Bibliography at the end, and many of these are sources (either directly or at second-hand) of the developments here set forth. To fit these into a continuous chain of deduction has involved considerable modifications from their original form, so that it has not generally been found practicable to indicate the sources of the separate sections. A frequent cause of deviation in treatment is the fact that in the view of most contemporary writers the Principle of Stationary Action is the final governing law of the world; for reasons explained in the text I am unwilling to accord it so exalted a position. After the original papers of Einstein, and those of de Sitter from which I first acquired an interest in the theory, I am most indebted to Weyl's *Raum, Zeit, Materie.* Weyl's influence will be especially traced in [several sections], as well as in the sections referring to his own theory.

I am under great obligations to the officers and staff of the University Press for their help and care in the intricate printing.

A. S. E.

10 August 1922.