Besides, this lacuna would manifest itself very quickly in further derivations, for the latter would violate the principle of reversibility and therefore that of uniqueness. If from _joyo_ were derived _joya_, from this adjective, analogous to _gaya_, one could derive inversely _joyeso_ = _joyo_, thus producing two names for the same quality (just as above _sano_ would have been synonymous with _saneso_). If from _kurajo_ (_courage_) were derived _kuraja_ (_courageous_), one could derive from the latter _kurajeso_, synonymous with _kurajo_. And, on the other hand, _kurajo_ being the substantive of _kuraja_, this word would signify both _courage_ and _a courageous person_. From want of a single suffix the whole series of derivations would become confused and illogical, just as in a chain of reasoning a single error, or in an algebraical calculation a single false equation, would lead to the most absurd conclusions. To sum up, one must take care not to derive a word directly from another, except when they both express the same idea (apart from the difference of their grammatical _rôle_ in the sentence). Consequently, whenever the sense changes, a word element must be added or disappear, in order to translate the modification of the idea. It is by virtue of this condition that the language will become the exact and faithful expression of our thoughts, and will conform to that indwelling and instinctive logic which, in spite of all sorts of irregularities and exceptions, animates our languages. In its system of derivation as well as in the rest of its structure, the international language is nothing but a purified and idealised extract, a quintessence of the European languages. The logic which holds sway there is not the Aristotelian logic of genus and species, but rather that logic newly constituted under the name of the _logic of relationships_, which is, however, as old as the world, since it lies, though obscurely, at the basis of the formative processes in our natural languages. That is the reason why the international language offers to philosophers a particularly instructive field of study. It is worthy of their interest in other respects. Not only does it offer to them, as it does to all men, a _medium of communication_ between all countries, but it furnishes them also with an _instrument of precision_ for the analysis and exact expression of the forms of thought, which is very superior, from the point of view of logic, to our traditional languages, encumbered as these are with confused and ambiguous expressions. It is their duty to contribute to the development and perfecting of a language which, without losing anything of its practical qualities, can and must realise by degrees the ideal of human language; if it is true that there _does_ exist an ideal in our languages, though hidden and irremediably disfigured by all sorts of anomalies. To quote a saying of Schuchardt, _Was die Sprache gewollt haben die Sprachen zerstört_.[5]