The promise of organ donation, from a simple blood transfusion to heart transplantation, holds a sense of wonder. The science and technology supporting these interventions sound exciting, the results seem amazing and, quite correctly, we are often left in awe of how wonderfully and marvelously God has made us.

At face value, organ donation is a compassionate and logical choice.

Although there is no direct scriptural reference to organ donation, Jesus' example and teaching seems to align with this. In Luke 10:30‑37, in the parable of the man left stripped and beaten on the road to Jericho, we are exhorted to help others and to restore them to life. The Bible also contains many accounts of intervention to extend life or improve its quality, like that of Jesus raising Lazarus from the dead, partly to give him more time with his family (John 11:1-44). Jesus Himself was the ultimate sacrifice, giving His life so that we may live. In principle then, organ donation is a good thing and a way to "love your neighbour".

Several organs can be transplanted quite successfully including the heart and its valves, lung, liver, pancreas, kidney, corneas, bone marrow and bone, skin, and in some cases even brain cells. In order for an organ to be useful in transplantation, its cells must be viable that is, still be able to function.

Once an organ is removed from its functional blood supply, its ability to remain viable depends on its energy requirements, which differ for each organ. For example, the brain can survive for four minutes, the heart about four hours and the cornea up to eight hours. The successful transplantation of organs from donors to recipients is therefore constrained by time. Establishing that the donor's death is irreversible is critical.

The advent of organ donation has made the definition of death an imperative, and has raised some ethical concerns. The definition of death is complex and has been debated in many spheres. For our purposes we will restrict our definition to how it pertains to medical science. Death was once defined by the cessation of a heartbeat and of respiration. This is no longer valid, since the heart and lungs can be "restarted" using CPR and defibrillation, or even replaced by transplantation.

Partly to deal with these issues, the concept of brain death was proposed in 1968 by a committee at Harvard Medical School, and defined by the criterion of irreversible loss of whole-brain function, making the end of consciousness permanent. In brain death, the body is basically "alive" and can continue to circulate blood, fight infection, and even gestate a fetus to birth, though it is dependent on artificial ventilation.

More recently, there have been arguments that the whole-brain-activity definition of brain death is too broad, and some contend that the criterion should be altered to "loss of cognitive function", where thought and personality are irrecoverably lost. As Christians, this is an important debate for us to watch and contribute to, as we cannot condone the termination of a life.

Under Australian law, there are two definitions of death: cardiac death and brain death. Cardiac death occurs when the heart stops beating and cannot be restarted. The brain is then starved of oxygen and eventually stops functioning. In brain death, the brain is injured (often due to trauma), becomes starved of oxygen and stops functioning.

Organ donors fill different categories. Living donors can donate organs like blood, bone marrow and bone and kidneys. They are not irreversibly harmed by the donation. In kidney transplantation, for example, a willing donor with two functioning kidneys will live a normal life after donating one kidney. It would be wrong to obtain organs by coercion from unwilling donors, as is reported in some countries.

Cadaver donors have an irreversible loss of respiratory and cardiac function, and brain activity. Theoretically, skin, bone, heart valves and corneas can be harvested from these donors. In practice however, only corneas are harvested, as the other tissues can be obtained from living donors, or in the case of heart valves, can be synthetic or from a pig.

People who are declared brain dead are the only donors from whom major organs such as the heart and lungs can be harvested. In Australia, fewer than 1% of people die in situations that would make this kind of donation possible. Before a person can be declared brain dead, at least two physicians ascertain brain function, including assessing basic reflexes and performing an electroencephalogram (brain wave test). In brain death, the person will not respond to any stimulus, unlike someone in a coma, and they will not recover brain function.

Once a person is declared brain-dead in a hospital, they can be maintained on life support systems until the organs are harvested. In Australia, the family of the deceased will always be asked to consent to organ donation, even if the deceased was registered to be an organ donor.

In some countries, fetal tissue from aborted babies is used for transplantation, such as brain cells in treating Parkinson's disease. Some argue that these tissues are being used from already aborted fetuses and do not harm any new fetuses. The danger in this thinking was demonstrated in a Canadian study, which reported that women more readily consider abortion when they know that the fetal tissues would be used in transplantation.

There are a large number of people on waiting lists for organ transplants. Donating an organ is an act of selfless sacrifice for another and dramatically improves the quality of life of the recipient. In 2012, 354 organ donors made it possible for 1,052 Australians to receive transplants and have a new chance in life. As Christians, we can support organ donation in cases with complete loss of whole-brain function, provided brain death is carefully determined according to the Australian criteria.

Family members are understandably shocked and distressed when a loved one is diagnosed with brain death. As this is almost always unexpected, relatives are usually unprepared for the situation. When they are then faced with a request for organ donation, a decision which may need to be made in a relatively short time period, one might assume it would compound their distress. Yet this is not always the case: if the loved one had expressed a wish to be an organ donor, either by an endorsement on his or her driver's licence, or via a previous discussion of the matter, the decision to donate may be more easily ratified by family members.

Another consideration is the wish to help others and to bring some good from an otherwise tragic event. Indeed, studies have confirmed the potentially beneficial effect of donation on the grieving process and long-term outcomes of donor families. There are some caveats — that the families be treated with respect and consideration, and not be rushed or pressured into making a decision; that they feel that the issue of brain death has been adequately determined and explained to them, and there was no hope of recovery; and that there is no possibility of the treating team altering the way their loved one was treated in order to favour possible transplant recipients. Families also find it helpful if they are informed of which organs have been donated and (in general but non-identifying terms) to whom they have gone.

As Christians we strive to live biblically and to reflect a Christian worldview. To do this, we need to contribute to discussions on issues such as the end of life, and be ready to support, advise and even decide for ourselves.