What is the position of the Catholic Church on organ donation for the purpose of transplant? What moral principles are involved? What would motivate one to be an organ donor?
Pope John Paul II sums up the position of the Church in these words:
[T]he Gospel of life is to be celebrated above all in daily living, which should be filled with self-giving love for others. . . . Over and above such outstanding moments, there is an everyday heroism, made up of gestures of sharing, big or small, which build up an authentic culture of life. A particularly praiseworthy example of such gestures is the donation of organs, performed in an ethically acceptable manner, with a view to offering a chance of health and even of life itself to the sick who sometimes have no other hope (Evangelium Vitae, no. 86, original emphasis).
There are many kinds of organ transplants. The types relevant to the question are inter vivos and postmortem (cadaver) transplants.  Inter vivos transplants refer to those that take place among the living. They would include a donation such as bone marrow. Postmortem transplants refer to donations given after death. These donations typically involve an organ necessary for sustaining life. These would include donations such as a heart, lung, liver, or kidney.
Since the time of Pope Pius XII, the Church has explicitly stated that both types of transplants are licit, based upon the principle of fraternal charity, but only when certain requirements are met. Remembering that the end does not justify the means, these requirements include:
As the Catechism of the Catholic Church explains:
Organ transplants are not morally acceptable if the donor or those who legitimately speak for him have not given their informed consent. Organ transplants conform with the moral law and can be meritorious if the physical and psychological dangers and risk incurred by the donor are proportionate to the good sought for the recipient. It is morally inadmissible directly to bring about the disabling mutilation or death of a human being, even in order to delay the death of the other persons (no. 2296).
Inter vivos donations
In every instance, inter vivos transplants (vital homografts) demand answers to serious ethical and moral questions. Because these donations require a transplant from one living person to another, a moral dilemma involving the principle of totality arises. According to this principle, the parts of the body are ordered to the good of that specific body. Therefore, the surgical mutilation of a donor for the good of the recipient must not seriously impair or destroy bodily functions or beauty of the donor. 
For example, both eyes are necessary for certain visual functions. A living person would seriously impair his ability to see if an eye were donated to another. Such a sacrifice would detract from the wholeness or full functioning of the donor's body. It would be a bad means to a good end, and therefore morally wrong.
Some argue that each person has a right over their body to provide self-sacrifice for another in need. They cite people who gave their lives to save another, like St. Maximilian Kolbe. The analogy fails. Kolbe and others freely accepted death, but did not choose death. They did not end their own life. Rather, these martyrs accepted death so as to save another's life. In contrast, an organ donor does choose to impair or destroy bodily functions within himself by transferring these functions, via transplant, to another. 
Based upon the law of fraternal charity, one may intend to sacrifice an organ for the sake of another, but one also has the responsibility for the integrity of one's body. Therefore, the principle of totality sets limits on inter vivos organ donations. Otherwise, inter vivos transplants could lead to euthanasia or assisted suicide.
Regarding postmortem donations, the moral issues revolve around a definition of death. For a postmortem donation to be morally acceptable, those involved must have certain proof that death has occurred. It is forbidden to cause the death of a donor because of organ transplant, even if his death is inevitable due to natural causes. With this in mind, there arises certain objections to organ donation even with informed consent from a patient or nearest of kin:
To protect against these dangers, three conditions must be met to justify a postmortem donation. (1) The donor must be verifiably and legitimately dead; (2) Proper, informed consent must have been given by the deceased donor with verification from a trustworthy source. In the absence of previous consent by the donor, consent of next of kin is admissible, provided that the deceased would not have opposed it; and (3) The remains of the donor must be treated with the same respect consistent with what was until death, and will be again, a temple of the Holy Spirit. 
The United States Catholic Bishops' Conference stated in 1977:
The transplantation of organs from living donors is morally permissible when the anticipated benefit to the recipient is proportionate to the harm done to the donor, provided that the loss of such organ(s) does not deprive the donor of life itself nor of the functional integrity of his body.
Postmortem examinations must not begin until death is morally certain. Vital organs, that is, organs necessary to sustain life, may not be removed until death has taken place. The determination of the time of death must be made in accordance with responsible and commonly accepted scientific criteria. In accordance with current medical practice, to prevent any conflict of interest, the dying patient's doctor or doctors should ordinarily be distinct from the transplant team. 
A culture of death
Powerful medical organizations that advocate organ donation do not always support the morally correct position. Take, for example, the flip-flop stance of the Council on Ethical and Judicial Affairs of the American Medical Association (E-J Council AMA). In 1988, the Council concluded that it is "ethically acceptable" to use organs from anencephalic  neonates only after they have died (AMA "Reports," 1992, vol. 1, 40-52). In 1994 the same Council reversed its position by stating that it is ethically acceptable to transplant the organs of anencephalic infants even before they die.
The rationale for the reversal, while noting that what they advocate is illegal in most jurisdictions, was published in a Council report on "The Use of Anencephalic Neonates as Organ Donors" in the Journal of American Medical Association (JAMA) v. 273, no. 20, 1614-18. Their reasons are:
The AMA is arguing that the fetus is deformed and lacks almost all brain tissue so that it is only doubtfully human. However, speculation is irrelevant in the Catholic context. There is no doubt whatsoever that this fetus is fully a human person. Nonetheless, the AMA's "doubts" as to whether such a fetus is "human" includes the willingness to destroy it "even if" it is human. Therefore, removing the organs of an anencephalic infant incurs the moral malice of murder.  How or why are doctors of medicine best able to determine who has "no interest" in living? "Is it even a question of medicine to ask, much less answer, which life (or lives) have no value in themselves but only for others?"  Both law and ethics require that a person be dead before his vital (life-necessary) organs be taken. All the objections listed earlier have merit, but the first objection has primary importance. The procedure violates the prohibition of removing vital organs from living persons!
Promoting the Gospel of Life
The argument about anencephalic infants is important because it serves to show the progressive anti-life movement not only within the medical profession, but within our society as a whole. Our current culture, dubbed the "culture of death" by Pope John Paul II, is echoing similar currents to those of pre-Nazism. A culture that makes the choice to select which member is or is not worthy of life is "playing God." This is stating that individuals of a society only have value insofar as their life is useful to society. When an individual's life no longer has value, then only his body parts have value and not the person as a whole. If this thinking continues to prevail, it is only a matter of time until the laws of our country embrace euthanasia and assisted suicide as permissible in every place.
The true purpose of an organ donor is to be "[a] particularly praiseworthy example [of the Gospel] of Life." However, organ donation in today's culture is misconstrued by those who support the "culture of death." With the recent opinion noted by the AMA, the door is now open for the medical profession to "play God" in yet another way. Allowing the removal of necessary organs from persons in persistent vegetative state and patients with severely disabling conditions violates the natural right to life. If the person killed has not given consent, he is not morally liable for the act, but those giving the consent and performing the acts are.
In order to protect their own life and promote the Gospel of Life for all, organ donors and those who survive them have a grave responsibility to practice and promote the moral teachings of the Church. If you are a card-carrying organ donor or in charge of deciding whether someone's organs ought to be donated or removed, beware! Organ donation is justifiable on the principle of fraternal charity, but within the limits of the principle of totality. Within these limits, organ donation can witness to the Gospel of Life. Last edited: 12/00
Faith Facts. "Play It Again Organ Donation." Lay Witness (January/February 2001).
Reprinted with permission of Lay Witness magazine.
Lay Witness is a publication of Catholic United for the Faith, Inc., an international lay apostolate founded in 1968 to support, defend, and advance the efforts of the teaching Church.
Copyright © 2001 LayWitness