It is to be built here, under the roof of St Stephen’s Church – with the return of this most charismatic venue to Fringe use – among a new generation of fervently aware feminists, as encouraged by Nic Green’s blazingly powerful Trilogy (*****).

Men and women, some of the latter now voluntarily naked, we sing Blake’s words as if discovering them for the first time. It’s a moment of shared experience that is moving and joyful, and it’s hard to put into words. Tears come more readily … as do the whoops and hurrahs.

Glasgow’s can-do stronghold of radical work, the Arches, has re-opened the doors on what was, until last year, home to the Aurora Nova programme of physical theatre and performance. The “official venue launch” of

Arches@St Stephen’s is at 2pm today: turn up and you’ll get a flavour of the free-wheeling enterprise that artistic director Jackie Wylie and her team regard as standard.

There’s an Artists’ Bring and Buy Sale, for example. It’s ­tempting to imagine this as a swap-shop where you can trade Fringe artists you don’t like or want for someone better – but instead, like the Bring Your Own Bottle policy in the cafe, it’s part of the Arches’ strategy to support the cash-strapped performers who stake their all on coming to the Fringe.

Conflux are staging an outdoor durational performance until 5pm, so expect some crafty ­mayhem to stop you in your tracks as you head for the box office. Two shows – ­Spaceman (****) and the aforementioned Trilogy – are in the main space at 5.30pm and 7.30pm respectively, and after that (at around 10.30pm) there’s the first of ­several Scratch Nights, where various artists try out ideas before a live audience (for free, but donations at the door are welcome). The aim, throughout August, is simply to have the building buzzing with creative energies, and there’s a whole roster of late events lined up with that in mind.

Right now, though, there are two compelling reasons for making your way to Arches@St Stephen’s, namely Trilogy and Spaceman. The latter, from Dudendance Theatre, is a solo odyssey devised, written and performed by Paul Rous and directed by Clea Wallis.

It opens with a disconcerting glimmer of white, moving out of the darkness that frames the now-silent church organ. A figure in long-skirted period frock and bonnet hovers towards us before, in the first of a series of morphing episodes, “he” emerges from the carapace of “she” like a new life-form entering into the process

of evolution.

Rous is a tall, well-muscled figure, who slips persuasively into knuckle-dragging, gorilla mode. But he also has a perhaps unexpected delicacy at his fingertips; a light springiness of step and a crisply nuanced precision in the smallest of details that together carry him through to the robotic state he envisages as our future. At the same time, he weaves in another strand – a mix of Nasa facts and sci-fi imaginings – to show humanity, in the shape of a young, inexperienced astronaut encountering an unknown alien intelligence …but can he prove this? The final moments, which I’ll not give away, suggest a how and why behind our own mutations.

The slow, intense unfolding of Rous’s vision demands an audience’s concentration, but it rewards thoughtful attention with images and ideas that encourage the imagination to fly off in interesting tangents. And the eerie, still quality of the space suits the piece admirably.

Having seen the individual parts of Trilogy at different times over the months of its development, I reckoned I knew where it was coming from – Nic Green’s curiosity about what it means to be a woman today – and where it was going, namely to that closing massed chorus of Jerusalem that uplifts and urges us to change society, not just to a better realm for women but for everyone.

Even so, the cumulative effect of all three pieces running end-to-end (with interval breaks) was an unexpectedly emotional and intellectual whammy – hilariously funny, charged with raw honesty and serious intent, and graced with ­generosity of spirit not only on the part of Green and her collaborators but from the women participants who turned up, stripped off and danced in the joyful fullness of their naked flesh.

Across all three parts, Green, aided and supported by Laura Bradshaw with Louise ­Brodie, Murray Wason and Jodie ­Wilkinson, uses themes from the feminist tracts and theories of the 1970s (before she was born) as a springboard for exploring issues of body politics, freedom of choice, personal identity and the influences and circumstances that maybe make us feel we’re liberated … but on whose terms?

What is especially fine about her research and the work that now comes on stage is that Green isn’t interested in diatribes of grudge and resentment. Instead, what emerges is a sense of how the past informs the future, if we take time to look back as well as forward.

Part two – Town Bloody Hall – uses archive footage of the famous 1971 debate chaired by Norman Mailer. But as Green and the ­others blend in their own responses to what was said then – with Wason musing on how he’s not Mailer-man, but that he can’t dismiss the possibility of such arrogant, misogynistic traits lurking in the depths of his psyche – the sheer stature and integrity of what these performers are doing is inescapable, and hugely moving.

They want to understand how we got to where we are, not in terms of techno-gizmos but in terms of our aspirations and ­compromises. They want to connect with history, but not be hag-ridden by it. They chat. They dance – often naked and innocently, in little gestural rituals that aren’t narrations but feel meaningful. Green’s own utterly beguiling, resolute cheeriness, complemented brilliantly by Bradshaw’s own humorous disposition, might belie the profound nature of the work, but actually it makes some tough thinking accessible and entertaining.You won’t see anything quite like this anywhere else on the Fringe. Just buy the ticket, and find a blistering, radiant ­Jerusalem at St Stephen’s.

Both shows end August 31. Adrian Howells: Foot Washing for the Sole runs from August

25-29 (various times).