‘I envision a world in which a person with multiple disabilities can be euthanised, with an agreement from the guardians, when it is difficult for the person to carry out household and social activities.’ These are the words of Satoshi Uematsu, the 26-year-old man who killed 19 disabled men and women in a care home in a Tokyo suburb last month, in the biggest mass murder Japan has seen since the Second World War. In a letter to the speaker of Japan’s lower house of parliament in February, Uematsu explained his motives: ‘I believe there is still no answer about the way of life for individuals with multiple disabilities. The disabled can only create misery. I think now is the time to carry out a revolution and to make the inevitable but tough decision for the sake of all mankind. Let Japan take the first big step.’

Uematsu didn’t cite Peter Singer, but their reasoning isn’t totally dissimilar. In Practical Ethics (1993), Singer argues that disabled infants can be euthanised with the consent of their parents whenever doing so would increase the total sum of happiness – this applies not only to infants whose disabilities would make their lives (to use Singer’s phrase) ‘not worth living’ but also to infants with conditions that are obviously compatible with flourishing lives, such as Down’s Syndrome, but who (in Singer’s estimation) have lives ‘less worth living’ than non-disabled people. ‘Killing a disabled infant is not morally equivalent to killing a person,’ Singer writes. ‘Very often it is not wrong at all.’

On Australian television earlier this month, Singer was asked by the disability rights activist Kath Duncan whether his philosophical advocacy for euthanising infants serves as a dog-whistle to people like Uematsu, who wish to exterminate disabled adults. ‘Not at all … What I’m doing is trying to give parents a say in questions where they’re the ones who are going to be forced to look after this child whether they want to or not,’ Singer responded. ‘It is not some crazy guy going into a unit and killing people.’

No one seriously thinks that Singer endorses what Uematsu did, at the very least because Singer rejects involuntary euthanasia for disabled people who are capable of consent. The question is whether Singer’s utilitarian treatment of disability fuels and gives cover for an already widespread hatred of disabled people.

In Practical Ethics, Singer showed more sensitivity to the distinction between an argument and its likely effects, anticipating the worry that euthanising disabled infants would lead us into the ‘abyss of … mass murder’. He reassured readers:

There is, anyway, little historical evidence to suggest that a permissive attitude towards the killing of one category of human beings leads to a breakdown of restrictions against killing other humans … All of this is not to deny that departing from the traditional sanctity-of-life ethic carries with it a very small but nevertheless finite risk of unwanted consequences.

Read more in the London Review of Books

Amia Srinivasan: The New Utilitarians · 24 September 2015

Thomas Nagel: Euthanasia · 6 October 2011

Judith Butler: The Death Penalty · 17 July 2014

Martha Nussbaum: If Oxfam ran the world · 4 September 1997