From @Baloo Commentarial Inerrancy - #18 by Dhammapala
The Abhidhamma’s explanation of consciousness and mental factors operating at the ultimate level, independent of conventional language designations, provides the foundation for understanding why Māgadhī is the natural language. When consciousness manifests its expressive capacity without external linguistic conditioning, as the Sammohavinodanī demonstrates through the example of a person born in isolation, it naturally does so in Māgadhī. This indicates that Māgadhī most closely corresponds to the actual structure of ultimate reality (paramattha), which explains why it emerges spontaneously when untainted by conventional linguistic influences and why it is the language chosen by all Buddhas to express the Dhamma.
Venerable Bhadantācariya Buddhaghosa remarked that Pāli (By referring to it as Māgadhabhāsā), is “easy to convey the meaning” (atthaṃ āharituṃ sukhaṃ hoti, literally: “it is simple to bring forth the meaning”). He further noted that “as soon as the sound reached the ear, the meaning appeared in countless ways, in myriad forms” (sote pana saṅghaṭṭitamatteyeva nayasatena nayasahassena attho upaṭṭhāti, Vibh-a 718).
This leads us to affirm that Pāli is a “natural language” defined within natural terminology (‘sabhāvanirutti’),