It is one of the eligibility criteria of the bill that the person seeking to end their life must be in an advanced state of irreversible decline, meaning they have lost the ability to live a full life.
Seymour said that was not a judgment on anyone's ability.
"Look, I don't normally talk about it but my mum had polio, my cousin has Down Syndrome and that means that in some ways they have a different level of ability from other people but they would not qualify for this bill because neither of them could ever argue that they were in an advanced state of irreversible decline," he said.
"Nobody by dint of having any kind of disability alone will ever be able to access assisted dying under this bill."
Donnelly said the bill was not needed and would not improve the quality of palliative care.
"This bill exposes the vulnerable. As doctors we are deeply concerned about the risk of legalising euthanasia to vulnerable patients in our society.
"The law is there to protect the vulnerable. Any change in the law which weakens this protection is unacceptable to us as doctors," Donnelly said.
She said it was not intolerable pain that drove people to euthanasia but feeling they were a burden or loneliness.
"Euthanasia is not an answer to society's disease of loneliness."
English said dying was scary. "It is the ultimate loss of control. You'll never legislate that away.
"The debate isn't really, in the end, about whether people are in extreme pain. It's actually … better educated more articulate people who are used to control in their lives who want the comfort of knowing that if they get into that situation, then they'll have an option to be able to take it early."
Even if people believed people had that right, it had to be weighed up against the consequences for everyone else.
Butler said he initially was not a supporter of assisted dying.
"If you had put a microphone under my gob on Lambton Quay about six months before I was asked to act for Lecretia in her case, I would have been a person who would have been opposed. In fact, that's what I told Lecretia.
"As a result of being involved in the case I've changed my mind."
Butler said Justice David Collins made three critical findings in his decision in Seales' High Court case – not all pain can be managed by palliative care; many people suffered premature death, with 3-8 per cent of people who killed themselves each year terminally ill; and having a mechanism such as that in Seymour's bill gave people control.
Last night's debate, hosted by Wellington National list MP Nicola Willis, was the latest in a series being hosted by National MPs around the country. The debates have been drawing good audiences, with a similar debate in Gore earlier this week also attended by about 200 people.
Willis said she hosted the debate in response to the high level of community interest in the issues raised by Seymour's bill.
"These are complex issues with deeply held views on both sides," she said.
The End of Life Choice Bill has received a record 37,000 public submissions to the Justice Select Committee.
The Justice Committee is sending sub-committees around the country to hear from all those who want to make oral submissions. It is expected to report back in March next year.
The proposed law change would give people with a terminal illness or a grievous and irremediable medical condition the option of "requesting assisted dying".
"It allows people who so choose, and are eligible under this bill, to end their lives in peace and dignity, surrounded by loved ones."
English, who staunchly opposes euthanasia, appeared alongside his wife Lady Mary English, a Wellington GP, at the select committee earlier this year.
He called the End of Life Choice Bill bad legislation.
