Of over three hundred different schemes to which new ones are constantly added, only five have so far - and to a larger or lesser extent - demonstrated their usefulness in speech and writing. They are Esperanto by Zamenhof (1887), Ido by de Beaufront, Couturat, and the Delegation (1900-1907), Occidental by de Wahl (1922), Novial by Otto Jespersen (1928), and Latino sine flexione by Giuseppe Peano (1903).
Broadly speaking, these systems represent two different schools of thought (1) the autonomistic systems: Esperanto and Ido, and (2) the naturalistic systems: Occidental and Latino with Jespersen's Novial mid-way between the two. The autonomists say that in order to make our language as easy and as precise as possible, its elements shall be independent of the usages of ethnic languages. We must, they say, create a set of principles which will be carried out in our language without exceptions. Our language shall be regular and logical.
The naturalists say that in order to make our language truly international, it should resemble, as closely as possible, the existing forms of the ethnic languages, and preferably the Romanic group of languages. All elements and forms shall be natural. It is more important that our language, in speech and writing, be immediately understood, than that its forms, its elements, its rules, should be independent of ethnic languages or be based on a priori considerations. Any factor contributing to naturalness is desirable. Our language shall be naturalistic.
These different points of departure imply certain basic differences apparent in the structure of each system. I have selected merely one point which is, to my mind, of fundamental importance, that of direct and indirect derivation. The term derivation is here used to indicate the relationship of roots within one family, that is verbs and adverbs; nouns and adjectives. Derivation is not used to indicate the etymological origin of a word.