In the 1970s, the Australian moral philosopher Peter Singer, perhaps best-known for his book Animal Liberation (1975), began to argue that it is ethical to give parents the option (in consultation with doctors) to euthanise infants with disabilities. He mostly, but not exclusively, discussed severe forms of disabilities such as spina bifida or anencephaly. In Practical Ethics (1979), Singer explains that the value of a life should be based on traits such as rationality, autonomy and self-consciousness. ‘Defective infants lack these characteristics,’ he wrote. ‘Killing them, therefore, cannot be equated with killing normal human beings, or any other self-conscious beings.’

The thought of killing disabled babies is especially dangerous because the concept of disability often functions as a mere cloak, thrown over much uglier hatreds. In ‘Disability and the Justification of Inequality in American History’ (2001), the historian Douglas Baynton points out that African-American enslavement was justified through disability models: there was a supposition that African Americans suffered from a number of medical conditions that were understood to make them unable to care for themselves. Until 1973, homosexuality was a psychological disorder justified in the Diagnostic and Statistical Manual of Mental Disorders; the current edition, the DSM-5, still considers transgender people disabled.

Singer generally frames severe physical disabilities through a medical lens. His ideas chafe against models of the disabled as a minority group. To Singer, severe disability is more a problem to be solved than a difference to be embraced and accommodated.

For years, I thought Singer was morally bankrupt. I grew up in a family with hereditary deafness, and though deafness is far from the type of disability that Singer was focusing on (with some arguing that it’s not a disability at all), I still recognised an idea that the disability community has faced for centuries: that people with disabilities are fundamentally less entitled to their rights – even their lives. Singer’s ideas stood in opposition to my core belief that the disabled body is created largely through a lack of accommodation, and that people with disabilities are different perhaps, but not less.

While most of Singer’s other writings seemed so thoughtful, so compassionate, his writings on disabled children seemed to be approaching the slippery slope toward ethnocide – the intentional and systematic destruction of cultures, like the Deaf culture that my own family embraced. I had never been able to shake what he was saying about the disabled – and I wanted to know more: what he thought today; if his ideas had ever shifted; and, mostly, how he could believe so strongly in something that seemed so out of sync with his reverence for life.

This past winter, I reached out to Singer to learn more.

I was nervous to talk with him, even over the blurry, jumpy distance of Skype, but I had no reason to be. Though his ideas felt abrasive, even violent, to me, he took opposition with thoughtful consideration. And as we talked, I began to wonder if I hated his ideas because they poked at sore spots in my worldview, exposing its vulnerabilities.

Singer resists the idea that disability is mere difference; there is suffering involved, he says, and not only of the social variety. ‘I don’t think the idea that it’s better to be able rather than disabled is in itself a prejudice,’ he told me. ‘To see that as akin to racism or sexism is a mistake.’ He argues that if it weren’t preferable to be able-bodied, we wouldn’t have a problem with pregnant women taking drugs or drinking heavily, that avoiding disability would have to also be seen as prejudicial. It isn’t, and Singer maintains that it shouldn’t be.

Instead, Singer maintains that disability, unlike race or gender, comes with intrinsic suffering – sometimes great enough that it is more compassionate to end the lives of infants than to force them to live in pain. Over the years since he first began discussing this proposal, Singer has had to contend with studies showing that quality-of-life assessments of people with disabilities are not that different from those of able-bodied people – a fact that could grossly undermine his argument of alleviating suffering. While he has found those studies compelling, he maintains that it’s not fair to allow them to speak for those too severely disabled to respond to such a survey. (In general, he doesn’t buy the idea that people with vastly different disabilities ought to be speaking to each other’s experiences.)

Disturbingly, though he focuses mostly on severe disabilities, he also resists putting strict parameters around which disabilities would qualify for infanticide. ‘Look,’ he told me, ‘I don’t think it’s for me to tell parents [that] if your child is like this you are to end the child’s life, and if the child is like that you ought not to.’ Instead, he considers how class, family, community, not to mention regional and national support, shape the potential life of the child.

Particularly surprising was how Singer’s responses often revealed under-investigated issues in the disability movement’s rhetoric: the idea that class and location could have tremendous impact on a parent’s ability to raise a child with a disability, for instance, or that some are so disabled that they have no ability to speak to their own quality of life. The way that Singer’s ideas are often engaged with exhibits an intellectual laziness that tosses these issues dangerously aside.

Singer has not focused on infanticide for decades, but his ideas still ache in the disability world, like a wound that won’t heal. Singer is still deeply entrenched in questions about the hierarchy of lives, and his ideas about the inferiority of many people with disabilities – and the dangers that those ideas imply – are as pertinent today as they’ve ever been. The epidemic of spina bifida that spurred his arguments has now passed, but the larger questions he poses are still central to questions of prejudice and equality in the disability community. This makes it hard to sort through Singer. His arguments are built intricately and beautifully, like a perfect mathematics equation, but at their core beats a single assertion, one that is still too difficult to concede: that this group of human beings aren’t really people. That’s the pain that obscures the rest.