I am certain that an entire book could be written on this subject. Perhaps one already has, though I have not personally seen it yet. But my answers to these ‘troubled students’ is always one that seems to bring a new awareness to communicating through language that is quite foreign to the English mind set; It happens not because it’s convenient or succinct, but because it’s beautiful!
You see, the mind and culture of the Gael is far more concerned with beauty than with efficiency. The Celts have always been mindful of the beauties of nature and the ‘natural way’ that Nature itself seems to create. It is reflected in their art, in their poetry, in their society, and most especially in their language. That being said, these mutations also create sonic clues that communicate by rather direct means, very abstract and subtle ideas.
Gaelic mutates its words to generate phonetic sounds that are designed to ‘clue in’ the listener that something special or significant is happening. Most of the extreme phonetic clues appear in what we call the genitive case, but many smaller changes are scattered all throughout the grammar of the language. For example, any time a speaker is emoting about something that has already happened (a.k.a.- the past tense), that sense of time is conveyed within the first word of the sentence by the presence of lenition! Before any explanations about anything are given, the lenited verb ‘sets the listener up’ with its phonetic change that the speaker is talking about something in the past. This ‘set up’ is further reinforced by the grammatical placement of the verb as the first word in the sentence. Talk about direct communication!
However, these changes go way beyond simple ease of communication. There is also a strong aesthetic component as well. Sound mutations, most especially the art of slenderization, hard-wire the language for poetry use. Here’s an easy example. Let’s say that I have a poetic idea with a word that ends the line in a slender sound such as: Bha mi nam shuidhe aig a’ chidhe. And I want to say something about my hand, however, hand is làmh, which ends with a broad vowel. Well, I know that làmh is feminine, so if I place the word into the dative case (a.k.a.- a prepositional phrase) I can SWITCH its sound to a slender one! Now I can write:
Bha mi nam shuidhe aig a’ chidhe,
Agus mi a’ coimhead air mo làimh.
Bang! I have a rhyming couplet and I didn’t need to switch to a different word or change my original thought!
When we examine this kind of linguistic idea, we have to conclude that these complicated rules concerning spelling mutations that we have to learn in order to speak were NOT created because our Gaelic ancestors wanted a language that could say as much as possible in as few words as they could. No indeed. They were quite obviously concerned with the beauties of human speech and the wondrous way that we can communicate to one another using sounds, even at the emotional level! Now THAT is a deep thought…