The Church of England is in hot water with some evangelicals after it hinted it may support the genetic modification of human embryos.

The controversial method known as germline editing involves changing the DNA in an embryo to alter a baby's characteristics. The alteration could range from the eradication of hereditary disease to specifying a person's height. Although it has been around for a number of years, debate has intensified since 2014 as Chinese scientists began developing a new method to make germline editing cheaper and simpler. 

The Church of England has been careful not to explicitly support germline editing, but has clearly not ruled it out. 

In a blog published yesterday, the CofE's national advisor on medical ethics, Dr Brendan McCarthy, urged "all aspects of this topic" be rigorously investigated and debated before opinions are formed. However CARE have already made up their mind.

"In our view, endorsing genetically modified embryos is a mistake," said spokesman James Mildred. "We would encourage the church to think very hard indeed before giving its blessing to the modification of human genes."

So what are the key "aspects" McCarthy is urging be "thoroughly investigated and debated prior to opinions being formed?" Let's start with the basics:

What is germline?

Human genes are the basis of all the information needed to build and maintain our bodies. Genes, and therefore our hereditary traits, both good and bad, are passed on to the next generation through our sex cells (ovum for women, sperm for men). It Is these sex cells that are part of the germline.

What is germline editing?

It is a form of engineering whereby DNA is inserted, replaced or removed from a germline cell.

What is editing used for?

The purpose is to fix defective DNA. This would mean that unwanted hereditary traits would not be passed on to the next generation. In theory germline editing could cure genetic diseases such as HIV/AIDS, hemophilia and many others.

What is the current law?

Currently most researchers agree germline editing should be prohibited for the time being for safety reasons. It is banned in 15 out of 22 European nations and although it is not illegal in the US, the White House opposes it.

What are the issues?

As McCarthy said in his post, "Viability [the ability to safely do what is intended] is a necessary, but not a sufficient, pre-condition for action." Although the ethics are complex, "detailed questions must be asked and debated."

The main ethical considerations centre on the purpose and long-term impact of germline editing.

Is the purpose of editing to cure a disease (therapy) or to increase an individual's abilities (enhancement)? The worry is that the procedure could eventually lead to non-therapeutic genetic enhancement which is effectively a form of eugenics. The wealthy could use the technology to create "designer babies" whose genetic enhancements would not be limited to eradicating diseases but would determine their height, eye colour, intelligence, longevity etc.

The other concern is because the germline is being edited, the alterations will be passed on to future generations and may have unintended and unwanted consequences. In essence it is an uncertain experiment on future generations without their consent. As Mildred put it, "we simply cannot know the consequences of genetic modifications for future generations and this sort of experimental genetics could effect unborn generations as modified genes are passed down."

What are the main points I should think about?

The key difficulty is that the line between therapy and enhancement is becoming increasingly blurred. Generally therapy, curing a disease or fixing broken physical systems, is considered a good thing. However enhancement, the attempt to improve aspects of the body that are not broken in the attempt at "perfection."

But distinguishing between the two is often very difficult. Is short-sightedness, for example, a malady to be cured or an enhancement? The question inevitably implies that as humans we know how to improve our design and which aspects are essential and non-essential.

Another point to consider is whether the technique, which would inevitably cost large amounts of money, would fuel unjust inequality. Would those who are not able to be cured of genetic diseases or who possess undesired genetic traits, be treated differently? Would there be intentional or unintentional discrimination against those who cannot or will not edit their child's genes? CARE spokesman Mildred asked, "Do we really want a situation where people with more money could buy so called 'super babies' with money meaning 'enhanced features'?

Perhaps the most central consideration will be our "understanding of the nature of human life," McCarthy wrote.

"The danger," he said, "is that, from the outset, individuals and groups will be pressured into 'taking sides' either as 'cheerleaders' heralding progress or as 'Cassandras' bewailing the shape of the future.

"The issues involved are much too important to be reduced to visceral 'yippee' or 'yuk' reactions. Indeed, this debate gives all involved an opportunity to reflect on their ethical foundations; an opportunity too good to be missed in a rush to defend or promote existing presuppositions."

Whichever way the Church of England comes down, debate among Christians is likely to be divided.

"That is right and proper," said McCarthy, "but only if set in the context of a commitment to engage in a comprehensive, honest and informed examination of the scientific, social and ethical issues involved."

Watch this space.