International Auxiliary Languages or Philosophical Languages
Philosophical languages or international auxiliary languages, unlike most other conlangs are not derived from another language. This makes them a perfect language, as you are required construct an entire new set of words, or vocabulary. All philosophical languages are a priori languages, though the reverse is not always true. The main concept behind this kind of language is that in the schematic vocabulary, each word is preceded by initial letters that indicate its place in the semantic hierarchy of the language, hence the term a priori.
Emphasizing on categorization and classification, these languages also derived their name from the fact that they were first proposed by philosophers. Some of the more famous philosophical creators include John Wilkins, George Dalgarno and Athanasius Kircher. Using the smallest linguistic unit, having a semantic meaning, philosophical languages are mainly made of words that make use of a limited set of these units, known as morphemes.
Aimed at being closest to absolute perfection, these languages are based on transcendent truths, rather than practical principles. Particularly popular during Early Modern times, theses languages were hopes of many creators of recovering the ultimate language, the Adamic or Divine language.
With logical languages, or loglangs, gaining mileage in today's time, examples of philosophical languages can be seen mainly in the past. Some of the more popular philosophical languages include, the language by John Wilkins, presented in his book, 'An Essay towards a Real character, and a Philosophical language', 'Logopandectesio', Thomas Urquhart's attempt at an universal language, 'Ars signorum', the language of signs by George Delgrano amongst many others.
If you have a keen interest in this field, then reading works of earlier masters would be a good start. Also visualizing the purpose of your philosophical language is essential, as you have to ensure that your language is not derived from any existing language, which is quite a task. Requiring a lot of time and effort, philosophical languages are rare today, and your own creation could change the way humans perceive language and grammar. An active imagination and a clear goal are the two essentials for creating your very own philosophical language.