When I was a boy and I attended (note the past tense) my local church amid the council estates of a Scottish New Town, the building we went to had long become overfamiliar to me even by the time I learned to look around and realise that buildings were different at all, and that they might have been made with a higher purpose beyond simply what went on in them.

Within the high, white-painted brick walls and the angular wooden pews worn round-edged by decades of worship (even though the building was a brutalist post-war affair built in the 1950s in the spirit of Le Corbusier, and very young for a British church of most denominations), there was nothing left to surprise me in the way an adult walking in there today might be astonished by the oddness and ambition of the space. Yet one thing puzzled me. Above the altar, the bright, sheer brick walls continued as far as could be seen from the pews into the tower, uninterrupted; yet a beautiful, warm light rained down. Where did this impossible light come from?

As an adult, I discovered this church I no longer went to had played a small but key role in the recent architectural history of Scotland, as the first significant project finished by the architects Andy MacMillan and Isi Metzstein after assuming creative control of the esteemed Glasgow firm of Gillespie, Kidd and Coia. I thought about this church again just the other week, and about the way it continues to play a living role in its community through coffee mornings and jumble sales, after I'd heard of the ongoing sad fate of MacMillan and Metzstein's dying masterpiece.

A week ago the focus was entirely on St Peter's Seminary in Cardross, near Helensburgh, and the disheartening news that the closure of Angus Farquhar's pioneering public art organisation NVA meant that any hope of imminently reviving the space, as Farquhar had planned, as a partially regenerated artistic venue and retreat in the countryside was now dead. Yet anyone who saw NVA's 2016 work Hinterland, the art project which transformed the old concrete of St Peter's into a nocturnal dreamscape brought alive by light and dance, will be well aware how unique, how stunning this building is.

NVA's Hinterland / credit: Alasdair Smith

Now that NVA are gone, who will stand up for it? Who will save it? These questions have taken on a whole new impetus now the seminary's plight has been overshadowed by the sad fate – again – of Glasgow School of Art's Mackintosh building. This isn't the place to repeat the endlessly tedious online conspiracy theories about the blaze, or to second-guess fire investigations and insurance claims in apportioning blame. Yet the Mack has the reverse of St Peter's problem. Everyone wants to stand up for this internationally-recognised symbol of Glasgow, to claim ownership and demand restoration or renovation no matter what. Amid the squabble of voices, who's saying the right thing? Who's standing up to be counted and not just to be heard?

Although, while sympathy is widespread, not everyone is in favour of the Mack's automatic rebuilding. Behind the clickbait headline slapped across the top of it, Daily Record columnist Annie Brown's piece ('Spending £200m on Glasgow School of Art is vulgar when city's kids live in poverty') made a sensible and accurate point about the disinterest the city seems to take in its other architectural prizes in comparison to Mackintosh ('A motorway runs past the front door of the baroque splendour of the Mitchell library in Charing Cross,' she says. 'The legacy of Glasgow's other great visionary architect Alexander 'Greek' Thomson has been left to rot or worse, razed to the ground…'). Also worth a read on this subject, while you're at it, is Peter Geoghegan's Twitter thread on 'the appalling state of Glasgow's public realm.'

Yet sadly, such worthwhile and necessary comment was followed up in the Record with an arbitrary and meaningless poll of 1000 internet responders which fell 60% against public funds being used to restore the Mack ('Poll shows most Scots don't want taxpayers' cash spent on Glasgow School of Art rebuild,' loudhailered the headline authoritatively). And so a narrative of false equivalence develops that the full cost of a rebuild, £100m or even £200m, would be directly snatched from the mouths of people in poverty, rather than largely gathered from private donors – big businesses and individuals like Brad Pitt – once more, and the rest most likely drawn from the government's arts funding pot for the next few years.

Isn't it perhaps the case, then, that the people who may feel the greatest pinch of a Mackintosh rebuild are the artists who suffered during the last round of Creative Scotland funding? People like Farquhar and NVA themselves, in fact. So maybe the more sensible question to put to the people is, 'Do you know how projects like this are funded in the first place, with lots of money coming from private donors from around the world and so on, and do you know how much the government would have to spend on it and what they REALLY would have spent it on otherwise?' Then we can start talking about whether it's worth it.

Which is long-winded, of course, but things like this aren't simple and we shouldn't pretend they are. To claim the fate of the Mack's a simple matter of class divide is a tawdry gimmick, and if many people who live in other parts of Glasgow feel the building and the Art School mean nothing to them and that it's part of a culture they're excluded from – and it's hard to blame anyone if they do – then we shouldn't take as inspiration the current, fees-driven nature of higher and further education, but what Mackintosh's Art School meant to Glasgow for the majority of its existence.

This was a place where the working classes could go to explore new avenues in life, where men left jobs on the docks of the Clyde and women escaped the limited roles open to them throughout much of the 20th century in order to dream of doing - of being - something better. Take Metzstein and MacMillan, who both studied at GSA; one a Jewish refugee from Berlin who was fostered by a family in Clydebank, the other the son of an unemployed Maryhill railway clerk. MacMillan was on a Council apprenticeship when he arrived at the School and went on to become the head of its architecture school.

At the moment, what are the opportunities for local scholarships, for schools engagement, for community outreach at GSA? Perhaps, to truly claim to be an institution of its city in a way no other Scottish university can match, it should look seriously at visibly and vigorously promoting these elements.

Image from Robert Perry @rabperry on Twitter.

Incredible capture but such a sad day.

A post shared by ☰ M A R C ☷ (@_marc.andrew_) on Jun 16, 2018 at 2:58pm BST

In the days after the fire, a friend posted on Facebook 'Less heritage, more art', and that seems like a slogan which Mackintosh himself would have approved of. In recent years, the Glasgow Miracle which has seen all those artists from the city end up on Turner Prize shortlists has largely (but not exclusively) been facilitated by the school's MFA course, and this year the course's excellent degree show was held in the Glue Factory, a dingy, derelict industrial building next to a cash and carry and a plumbing warehouse on the other side of the M8. Art becomes heritage when it's been around for long enough, but the creation of great art doesn't rely on a beautiful building to facilitate it.

In an intervention which didn't go down well with many GSA alumni, but was at least strikingly well-argued, Professor Alan Dunlop made the case that the Mack should not be rebuilt, but should be the subject of an international competition to create a new landmark building. It feels hard to make any prediction of what will happen until investigations and costing are complete, but it is possible to make one demand of all involved with blanket certainty… Whatever you do now, don't do something shit. Just don't.

If the space occupied by the Mack is filled with student flats or a generic prefab sandstone blocks with coffee shops and supermarkets at street level in five years, then those charged with taking care of Glasgow will have made a monumental mess. Much like St Peter's Seminary, lest we forget, because this stunning building can't be allowed to rot either, even if this just means Historic Environment Scotland taking charge of it and preserving what's there until the next NVA comes along. It's fair to say that Fiona Hyslop will have some big and far-reaching decisions to make soon, but the right ones are surely there with some creative thought.

Anyway, it was just a window. The impossible light. There was a window on the front side of the tower which you couldn't see from the pews, but which lit the altar with reflected light bouncing off the white walls. All pretty simple really, but that's what a good architect does; make you stop and think about the space around you, which reminds you where you are and what you're here for. We may not know where the light is coming from, but we notice when it's no longer there.