Loglan is a constructed language originally designed for linguistic research, particularly for investigating the Sapir–Whorf Hypothesis. The language was developed beginning in 1955 by Dr. James Cooke Brown with the goal of making a language so different from natural languages that people learning it would think in a different way if the hypothesis were true. Loglan is the first among, and the main inspiration for, the languages known as logical languages, which also includes Lojban and Ceqli.
Dr. Brown founded The Loglan Institute (TLI) to develop the language and other applications of it. He always considered the language an incomplete research project, and although he released many papers about its design, he continued to claim legal restrictions on its use. Because of this, a group of his followers later formed the Logical Language Group to create the language Lojban along the same principles, but with the intention to make it freely available and encourage its use as a real language.
Supporters of Lojban use the term Loglan as a generic term to refer to both their own language, and Dr. Brown's Loglan, referred to as "TLI Loglan" when in need of disambiguation. Although the non-trademarkability of the term Loglan was eventually upheld by the United States Patent and Trademark Office, many supporters and members of The Loglan Institute find this usage offensive, and reserve Loglan for the TLI version of the language.
Brown intended Loglan to be as culturally neutral as possible, and metaphysically parsimonious, which means that obligatory categories are kept to a minimum. An example of an obligatory category in English is the time-tense of verbs, as it is impossible to express a finite verb without also expressing a tense.
Also, Brown intended the language to be totally regular and unambiguous. In particular, phonemes that could be confused with each other were to be avoided.
The language’s grammar is based on predicate logic, which is why it was named Loglan, an abbreviation for "logical language". This has been thought to make it suitable for human–computer communication, which led Robert A. Heinlein to mention the language in his science fiction novel The Moon Is a Harsh Mistress (1966), and as a fully-fledged computer language in The Number of the Beast (1980).
Loglan has no distinction between nouns and verbs. The predicate words can serve as verbs, nouns, adjectives or adverbs depending on where they occur in a sentence. Each predicate has its argument structure with places for arguments, which may be variables. For example: vedma, "X sells Y to P for price Q". Prefixes allow one to reorder the argument structure of predicates, to emphasize one of the variables by putting it first. For example, to make price the first variable, use ju vedma (with the "little word" ju). Similarly, the sentence can be reordered to speak about seller, ware, or buyer. Modifications for time, location, actor, type of action, and others are provided by "little words" which are optional. Predicates can be compounded: a predicate can act as an argument of another predicate, when the former is prefixed by a "little word".
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