As far as possible all systems have been treated in a uniform manner, giving a synopsis of their history, grammar, their principles of derivation and the affixes used, the methods of vocabulary selection, comparative texts, and finally a concise commentary representing the author's views. Some theoretical aspects call for special attention in the final formulation of a workable planned language; their implications have been discussed in Part II though it was not always possible to treat them without reference to other relevant problems. In Part III the practical attempts to arrive at a solution have been reported as far as they are known today; some of the technical data have had to be restated in order to present the problem of technical terminology in its proper perspective and setting. The book is therefore a work of reference rather than a report on interlinguistic development.
In the past it has been difficult to make comparative studies of the constructed systems from the limited material available, now mostly out of print. It is hoped that the following chapters be regarded as a basis for information which has not before been available except through the information of interested groups and societies.
The book is not intended to advocate any particular system or basic solution, but has been written, rather, as an analysis of planned language systems which have proved their usefulness in speech and writing, thus qualifying as a basis for further research and examination. It would be idle to expect that any one system evolved over the last fifty years is able to solve all demands of modern science or to answer fully the needs of modern society, and much exploratory work will still be needed to define, for example, the function and signification of affixes and the relation of certain principles to the ease of learning the planned auxiliary language.
While the subject of a planned language has not yet been accorded academic status, it is left to the individual and to interested groups to obtain the information on the various proposals from the limited number of books availble on the subject; the reader is urged to make as extensive a use as possible of the books mentioned in the bibliography.
For advice and criticism received I wish to thank Mr M. C. Butler, Mr A. E. Brighten, Harold E. Palmer, D.Litt., Mr A. W. S. Raxworthy, Mr Gilbert H. Richardson, as well as my wife for the revision of the MS and the encouragement received. I also wish to express my thanks to Dr S. Auerbach, Mr Robert S. W. Pollard, and Mr Gilbert H. Richardson for the loan of manuals , grammars, dictionaries and reports.