_This_ international auxiliary language, which forms one of the foundation stones of our general, scientific, and technical culture, is so closely bound up with the life and existence of science and has become so much the second nature of all scientific men, especially investigators, that they have long become accustomed to write and think in this language apart from their nationality. It is an easily ascertained fact, and one that is well known to the scientific men of all countries, that the latter can read foreign scientific literature much more easily than newspapers or novels written in the same languages. The explanation of this is that the foreign scientific works, on account of their technical vocabulary, are written in a language which possesses a much more international character than that of the novels or newspapers. It cannot, therefore, be denied that there actually exist already, particularly in science, the beginnings of an international (and largely artificially created) auxiliary language which is written, spoken, and read. We find here ready made the first provisional lexicon of the scientific international language. It cannot, therefore, be urged that science should "select" any one of the proposed artificial languages, because the selection of words is by no means an arbitrary process. The only procedure possible to science must be the construction of an international language on the basis of the already existing foundations. Science can never accept as an international language, one which destroys the actually existing internationality of scientific nomenclature. As we see, these considerations, like the former, lead us to the conclusion that the auxiliary language must be based on the principle of maximum internationality; that is to say, its vocabulary must be taken _à posteriori_ from the international treasury, and must not be invented according to any _à priori_ system or special idiom. It follows from this that the auxiliary language of the future must inevitably be chiefly Romance in its character, for Latin is the international auxiliary language which still lives and flourishes for, and by means of, science. The objection might be made here that the simplest solution would be the reintroduction of Latin into science as the auxiliary language. But this contradicts one of our fundamental premises, for Latin fails just as much as all other national languages to satisfy our second criterion, namely, that of complete logical precision. Besides, it is too difficult.