Cognitive Grammar (CG), in my opinion, is the premier theory within a cognitive linguistic scientific framework, exhaustive in its linguistic notions built up from general cognitive capacities, elegant in its fundamentals—merely three components: a phonological unit, a semantic unit, assembled into a symbolic unit, ie. form-meaning pairs—and comprehensive in its scope of linguistic explanation from word, meaning, syntax, on up to pragmatics, each level applying the same set of theoretical notions.
Humans are uniquely symbolic-based creatures, exploiting this complexity with the ability to talk, imagine, reflect, rationalize, and project ourselves and others in to the future. A grammatical theory that recognizes, and even makes central, a fundamental symbolic hypothesis for language, building up an entire infrastructure around it, taking seriously this human uniqueness of communication, with the success that CG has had over the past 40+ years in describing so many different languages, is worthy of any serious study and philosophical contemplation.
Some links for the not-so-faint-of-heart:
What is Cognitive Grammar (a helpful book for purchase providing basic details)
An integrated CG paper (a free PDF download of independent research on cognition that integrates with CG)