OXFORD UNIVERSITY PRESS LONDON OXFORD NEW YORK [verso] First published in the Home University Library, 1912 First issued as an Oxford University Press paperback, 1959 This reprint, 1971-2 PRINTED IN THE UNITED STATES OF AMERICA [Public domain (in the USA at least) HTML version completed February 1996. All copyrights for HTML enhancements are renounced. This is a freely reproducible text in the USA. In accordance with the differing copyright laws, in Great Britain (and others using the same copyright treaties) I understand it will become public domain 50 years after the author's death, that is, in 2020. (This may or may not be correct. They may have extended this another 20 years. Ask your lawyer before downloading into non-USA countries, or just hold off until A.D. 2040.) Companies mentioned above have nothing to do with this electronic edition. There may be errors not theirs. Please read at your own philosophical risk...