At a time when the language had only just been fixed and when he had very little practice in its use, L. Couturat translated into it a particularly difficult passage from the work of Gomperz (the Viennese Academician) on _Grecian Thinkers_. The present author, without having seen the original, retranslated it at Graz from the international language into German, and sent this to Gomperz at Vienna with the request, that he would give his opinion on the accuracy of the retranslated passage. Gomperz wrote characterising the reproduction as "astonishingly exact," "the test as extraordinarily successful, and the result in a high degree favourable to the possibility of employing the international language." This test must certainly be regarded as a very severe one, because the German language is foreign to the first translator, whilst, owing to its philosophical nature, the subject was not familiar to the second translator as a physicist. For the sake of English readers, a similar experiment has just been made, the results of which are given in Appendix III. A passage from Professor W. James's _Talks to Teachers on Psychology_, dealing with the laws of habit, was translated into Ido by Professor Couturat, and the Ido text retranslated into English by Mr. P. D. Hugon in London, who was unacquainted with the original. A comparison of the two English texts demonstrates the marvellous lucidity of Ido as a medium for the transmission of thought without distortion. Two things are indispensable for the realisation of a great idea. In the first place, the idea must, as regards its nature and value, have a rational foundation, and its possibility must be demonstrated. In the second place, there must be present courage, energy, and persevering devotion in order to realise practically that which has been recognised to be right and good. No amount of energy, however great, can produce a lasting result from a mistaken idea; but at the same time nothing great has ever been accomplished by doubters and pessimists. The readers of our brochure will concede to us that the idea of an international auxiliary language and its realisation by means of the language of the Delegation have in the foregoing chapters been fully examined in the cold light of reason and shown to be good and practicable, whilst the appendices will enable this opinion to be experimentally tested and confirmed. Now that the head has done its work, the heart, the source of courage and devotion, must do its part. We have full confidence, therefore, in calling upon the representatives of science, who have followed us so far, to assist us in the work, in the first place by _joining the Uniono di l'Amiki di la Linguo Internaciona_ and by making its labours known. This step can be taken also by those who do not see in the language as at present constituted the final and best solution of the problem, for before one can reach the topmost heights one must traverse the intervening stages. We ourselves do