The following work was written, and, except for some revision, in its present form, for the Gifford Lectures delivered at the University of Glasgow in the sessions 1916–18. The spoken lectures were based upon the book, but for reasons of time did not follow the text closely. I have accordingly omitted all reference to them in the division of the subject. I take this opportunity of expressing my thanks to the University of Glasgow for the honour they did me in entrusting me with the office of Gifford Lecturer; and to my audience for the attention with which they listened to me.
The substance of various published papers has been incorporated into the book, and in several places, notably in the chapters on Freedom and Value, passages have been repeated verbally with the kind permission of the editors of Mind and the Proceedings of the Aristotelian Society.
The first volume and the first two chapters of the second were in pages before the summer of last year, and accordingly I have made no reference to Mr. A. N. Whitehead's work on The Principles of Natural Knowledge, nor to Mr. Einstein's generalised form of the Theory of Relativity (the earlier restricted form I have ventured to refer to) which has lately become generally known in this country through Mr. Eddington and other exponents. The original papers of Mr. Einstein appeared in 1915 and 1916, and I saw the later one, but felt unequal to it without interpretation. In any case the physical theory is beyond my province, and the metaphysical theory developed in this book, which deals with the same topic but from a different approach, is best left to tell its own tale. But, as Bk. II. ch. iii. contains an apparent contradiction to one part of the new relativity doctrine, I have added a postscript to remove misapprehension, which the reader will find on p. vii.
Some suspicion is entertained of system in philosophy, though I can see no good reason for it. This book is at any rate an attempt at system, but its fault in my own eyes is not that it is systematic, but that it is not systematic enough. Parts of it I may hope to fill out with better knowledge and reflection, in which process I have no doubt that many things in it will need to be revised or abandoned. I am most concerned for the general outline.
Criticism does not occupy a large proportion of the whole, but I have not been able to dispense with it altogether, as I should have preferred. It is, at any rate, not introduced for the sake of criticism, for which I have no taste, but in order to make my own statement clearer. Naturally enough, most of it is directed against those writers from whom I have learned most, and may, I trust, be taken by them as a mark of respect and gratitude. My general obligations will be fairly clear. Apart from these, I have, I hope, indicated where I know myself to have borrowed from others; but there will be many places where I do not know whether I have done so unconsciously or arrived independently at similar conclusions. My work is part of the widely-spread movement towards some form of realism in philosophy, which began in this country with Messrs. Moore and Russell, and in America with the authors of The New Realism. It is, I think, matter for congratulation that there should be such marked differences amongst the independent workers; because there is better hope that something permanent may be reached amongst them.
My warm thanks are due to Mr. J. S. Mackenzie, who undertook the labour of reading the whole of my proofs, and gave me valuable comments; and to my colleague the Rev. S. H. Mellone, who read the book for me in pages. Several other friends have allowed me to consult them on special points, in particular Mr. T. P. Nunn, who did me a great service (not the first he has done me, by his writings or privately) by criticising certain chapters of the book, for which I can hardly thank him enough. I add that neither he nor my other friends are to be held accountable for anything I have written.
Postscript (to Book II. chapter iii.)
In the above chapter I have attempted to refer the category of universality to the empirical uniformity of Space-Time, and have expressed this feature by saying that Space is of constant curvature. This seems at first sight to be directly contradictory to Mr. Einstein's doctrine (in his generalised form of the Theory of Relativity) that Space is warped wherever there is matter, and the more so the nearer to matter, or in other words that Space has a variable curvature. The contradiction is, however, only apparent. When I say that bodies do not change their configuration by displacement in Space-Time, I mean this only so far as Space-Time itself is concerned. On the relativity theory too, Space-Time in which there is no gravitational field is uniform (Euclidean). A body may on the view of the text undergo distortion through its relation to other bodies, as in the familiar instance of the street-urchin who, eager for a cake in a confectioner's window, finds his nose flattened against the pane. And I assume that the presence of matter in Space-Time is properly represented mathematically by the idea of warping.
On Mr. Einstein's view, as I gather, bare Space-Time is merely a limiting conception, and there is no Space without matter. It is of course of profound importance for philosophy which of the two, material events or Space-Time itself, is regarded as primary. A similar topic has been touched upon in chapter vi. of Book I.