The terms “high-functioning” and “low-functioning” have no medical meaning. Nearly every expert I talked to referenced a common mantra in autism: When you’ve met one person with autism, you’ve met one person with autism. Which sounds nice, but is not particularly helpful when looking for meaning.

“With the spectrum, there’s a wide range, we’re still trying to figure out what that wide range means,” said Stephen Edelson, the director of the Autism Research Institute. “I don’t have a great answer. Scientific understanding of autism certainly continues to evolve,” said Paul Wang, the head of medical research at Autism Speaks. “I think there’s no one continuum necessarily,” says Lisa Gilotty, the autism-spectrum-disorders program chief at the National Institute of Mental Health. “It’s hard because ... different people will break that up in very different ways, I’m not sure any of those ways are accurate.”

“It’s almost like if you look in the stars in the sky and say, ‘Oh, there’s Orion’s belt. And oh, there’s the Big Dipper.’ You could also look at the stars and say they cluster a different way. And I think that’s still where we are with autism,” said Jeffrey Broscoe, the director of the population health ethics department at the University of Miami.

And perhaps because the spectrum has no agreed upon poles, there is very little data about how autistic people might be distributed along the spectrum. Different studies measure things like intellectual disability, and verbal ability, and self-injurious behavior in certain populations, but researchers know very little about what the autism population looks like as a whole.

* * *

Autism was not always considered a spectral phenomena. In 1938, the Austrian pediatrician Hans Asperger gave a speech before an group of Nazis. The patients in his clinic were largely children with autism, and he was worried that they might be sent off to Nazi extermination camps. So to convince his audience that they should be spared, he focused on his “most promising” patients. The ones that some would later call “high-functioning.”

But it wasn’t until the 1980s that the autism “spectrum” really took hold, thanks mainly to the work of a researcher named Lorna Wing. (Wing also rediscovered the work of Asperger and introduced the term Asperger’s syndrome, which was recently removed from the Diagnostic and Statistical Manual of Mental Disorders, the manual psychiatrists use to classify mental-health issues.)

Since Wing’s work first began, autism has become nearly inseparable from the idea of a spectrum. But like so much of psychiatry, autism is a construct, a conceptual framework that will sooner or later outlive its usefulness. And the spectral characterization of autism might work for now, but it might not work forever.

“Right now the best way to approach autism is to think about it as a spectrum condition, but it’s quite possible that in the next 10 to 15 years, we’ll start understanding these better—not just genetics but the real pathophysiology,” says Broscoe. One day it might be lots of different diagnoses, each pinned to a specific cause or mutation or biological breakdown. Just as people once thought of all cancers as singular, and now think about and treat breast cancer and lung cancer and colon cancer differently. Autism, Broscoe says, “may look more like cancer one day.”