How different are they both, fundamentally?

I know there are a lot of lexical differences and in the Hebrides they have Scandinavian influenced pre-aspiration, but would it be possible to make a koine language out of both?

Together they would be stronger

_________________
__̴ı̴̴̡̡̡ ̡͌l̡̡̡ ̡͌l̡*̡̡ ̴̡ı̴̴̡ ̡̡͡|̲̲̲͡͡͡ ̲▫̲͡ ̲̲̲͡͡π̲̲͡͡ ̲̲͡▫̲̲͡͡ ̲|̡̡̡ ̡ ̴̡ı̴̡̡ ̡͌l̡̡̡̡.___

pre-aspiration exists in all the dialects of Scottish Gaelic



take Rathlin Gaelic (which is now extinct but which was studied in a few linguistic books), it's half-way (a bit more Scottish maybe), or the late dialect of the Glens of Antrim, which is also half-way.



to me, the main thing that may cause problems in mutual understanding is vocabulary ; pronunciation is different but not enough to be a problem if they speak slowly enough. But many words are different or have a different meaning.
No need to make a koinè up... in my opinion

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

If you think the CO is unnatural, a koiné Gaelic would be worse -- it would literally be nobody's language.

The first difference is the number of tenses/moods. ScG has no simple present (using the future instead) and no habitual past (conditional doubles up for this, as in some Irish dialects).

Phonetically, the biggest difference isn't the preaspiration, but the heavy use of diphthongs, and then there's the Irish slenderisation of CH to GH in Irish, that only happens in southern Argyll (Islay, definitely) in ScG, and only in word-final position (IIRC). That leaves a lot of mismatches in the phonetic system.

The biggest issue I can see, though, is that the use of prepositions has diverged significantly between the two, and once you reach the phrasal level, this leads to notably different constructions:

Is Nìall an t-ainm a th' orm -- Is Níall ainm dom
Tha feum againn air -- Tá gá againn leis

In order to find something comprehensible to all speakers, you'd end up having to rely on English structures and words, which would kind of defeat the purpose of the exercise. And if it wasn't readily comprehensible, then why should Irish speakers spend time learning this artificial language rather than just learn Scottish Gaelic itself, and vice versa for Gaelic speakers and Irish?

_________________
A language belongs to its native speakers, and when you speak it, you are a guest in their homes.
If you are not a good guest, you have no right to complain about receiving poor hospitality.

if you compare:
Niall an t-ainm a tha orm
and
Niall atá orm

or
Is mise Niall
and
Is mise Niall

then it's not so different



If you say
Tha sin de dhìth orainn
and
tá sin de dhíth orainn

it's not different either



the future and present habitual share the same forms, same thing for past habitual and conditional. It's not the same as saying there's no present and no past habitual.



almost the same diphthongs exist in Munster Irish



that's right



I agree with you... Learning Scots Gaelic when u know Irish or Irish when you know Scots Gaelic is wee buns 2/3 of the work is already done

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

- Niall an t-ainm atá orm (the fuller form of 'Niall atá orm').

-Tá feidhm againn air (Maybe Ulster only).

I recently got full marks in an on-line SG test - not understanding much of it and not really having much idea of how to pronounce it either - but knowing how Gaelic functions, it wasn't a problem.

That's fair enough, but the "ainm dom" thing is one example of a fundamental pattern with that preposition, which is very different from the ScG.

_________________
A language belongs to its native speakers, and when you speak it, you are a guest in their homes.
If you are not a good guest, you have no right to complain about receiving poor hospitality.