A short introduction to glossopoiesis
7. Philosophical and logic languages
One possible motivation and goal for language constructors is to achieve an "exactness" which is far beyond the possibilities of natural languages.
For centuries, the meaning of exactness was categorization and classification. The whole reality was classified into a myriad of categories and subcategories (usually very abstract at the top level and more and more concrete in the further specifications), and each of these was assigned a code of some kind (a glyph, a letter of the alphabet, a number). The resulting languages differ from one another because of the different classificatory schemes and/or the different codes.
Such languages are called pasigraphies or, because they were first proposed by philosophers, philosophical languages. Among the authors of pasigraphies we may name Athanasius Kircher (1602-1680), George Dalgarno (1626-1687), John Wilkins (1614-1672), Augustin Grosseline (1800-1870), C.L.A. Detellier (1801-?) and Etienne D. Vidal (19th Century). In our time, a newly created pasigraphy called Babm (Fuishi Okamoto, 1962) has been proposed as an IAL, but it looks like nowadays pasigraphic systems have separated from the field of constructed languages to find a better place in bibliographic classification (cf., for example the so-called decimal classification originally by Melvil Dewey) and Internet directories.
Today's knights of exactness are logicians: their meaning of exactness is clarity and unambiguity, and their weapon is predicate logic.
The first person to suggest the possibility to create a unambiguous language based upon predicate logic was James Cooke Brown, father of Loglan. Loglan features a lexicon derived algorithmically from a number of source languages chosen among the most widespread languages of the world and a precise, unambiguous syntax based upon predicate logic.
Following a fracture in the Loglan community, some of the developers, under the guidance of Robert LeChevalier, founded the Logical Language Group and created Lojban, a reform of the language sporting a new lexicon, based upon a new algorithm and a partially different mix of source languages, and a revised syntax. After a period of study, the basic lexicon and the reference grammar of Lojban have been finalized and published, and the language seems to be gaining increasing consensus among those interested in logic languages.
New projects are still carried on. Some of them are admittedly inspired by Loglan and Lojban, such as, for example, Jim Carter's -gua!spi; some others are proposed reforms of Loglan/Lojban, such as Voksigid, proposed by Bruce R. Gilson and later abandoned.