A Twitter thread that undermines the core argument against abortion has gone viral causing a stir from those on both sides of the debate.

Science fiction author and journalist Patrick S. Tomlinson challenged one of the central notions used by ‘pro-lifers’ that life begins at conception, and that therefore, a human embryo holds the same value as a human child.

Speaking to his 25,000 followers, Tomlinson says that a decade ago he came up with a scenario which shuts down the idea, and that in all that time he’s never had an honest answer.

“Whenever abortion comes up, I have a question I've been asking for ten years now of the 'Life begins at Conception' crowd. In ten years, no one has EVER answered it honestly,” Tomlinson tweeted.

He goes on to explain a scenario whereby you are in a fertility clinic when the fire alarm goes off. Before you escape, you have the option to save either a five-year-old child who is pleading for help, or a container of 1000 viable human embryos.

“Do you A) save the child, or B) save the thousand embryos?“ he asks.

“There is no 'C.' 'C' means you all die.”

In a decade of asking the question, Tomlinson claims he has never had an honest response from people opposed to abortion.

“They will never answer honestly, because we all instinctively understand the right answer is ”A.“

“A human child is worth more than a thousand embryos. Or ten thousand. Or a million. Because they are not the same, not morally, not ethically, not biologically,” he tweeted.

“No one believes life begins at conception. No one believes embryos are babies, or children. Those who cliam (sic) to are trying to manipulate you so they can control women.”

Unsurprisingly, the moral conundrum caused quite a furore across the Twittersphere, provoking strong responses from those on both sides of the argument.

“I am a person of whom you describe. In this horrible situation, I would take the embryos. Save 1000 people verses 1. Isn’t it a no-brainer?” one man wrote.

To which Tomlinson replied, “Thank you for your honesty about being an amoral monster who should never be allowed around children. That was very brave of you.”

Another person, clearly pro-abortion, added, “They’re not even pro-life most of the time because they don’t want to help after the child has been born. They’re pro-forced childbirth, nothing more.”

The series of tweets spread rapidly with the original post having had more than 60,000 likes and 30,000 retweets since last week.