He applied it particularly to young people and those in psychiatric hospitals but, in 1972, UK art critic Roger Cardinal coined the term outsider art, expanding on Dubuffet's definition to include self-taught or naive art makers who hadn't studied at art schools.
Shepherd, who's championed our outsider artists overseas, says it's a problematic term for a field of art that's constantly evolving.
"It's art by people who haven't been influenced by the culture of art schools and institutions; they're not being strategic when they create," he says. "You won't see them referencing McCahon or slipping a koru into the corner of a painting.
"It's someone who's creating their own visual language and that's exciting. Andrew, for example, has come up with a graphic language that's very much his own and that's what I am looking for in good contemporary art."
New York has held an outsider art fair since 1993 but it's just the second time Auckland has hosted such a fair after a successful inaugural event in 2014. Van Asbeck says this year's programme is much expanded.
Some 40 exhibitions take place in shops, dealer and community galleries involving about 30 artists. They include representatives from Arts Project Australia along with locals Blythe, ceramicist Robert Rapson, Lauren Lysaght and Sam Taare.
"It's called an outsider art fair but we're about being inclusive and inviting in more people to see it for themselves," says van Asbeck.
Toi Ora has won awards for its work which focuses on arts programmes for those living with mental health issues. Van Asbeck says there's a tendency for some to be patronising about such spaces.
"People think of 'creative spaces' as nice and a bit quaint, doing a public good by keeping people busy, but creative spaces are so much more than that. It's about creating art that contributes to your community and is part of an internationally recognised contemporary art scene."
Thursday's launch party featured work by fashion designer Jeanine Clarkin who printed artists' work on to fabrics for garments worn in the show and yesterday artists gathered at Ponsonby's Studio One to discuss how creatives and marginalised people can contribute to Auckland's urban planning.
That's part of the community-led installation Dream Home where drawings by trained and untrained artists and the community are on display at Studio One showing what their ideal "dream homes" look like.
Van Asbeck says by using places like clothes shops as pop-up galleries, it will bring outsider art to the attention of more people. For Andrew Blythe, the fair is a chance to do what he likes best: make work and see it on display.
See nzoutsiderartfair.co.nz for the ArtExplore art trail map.
What: Outside Art Fair
Where & when: Various venues throughout Auckland until Saturday, November 26