Let's begin with a brief description of terms used by the media as they have covered this tragedy.

"Euthanasia" is derived from the Greek word "eu" (well) and "thanatos" (death). It usually means a "good death" or "mercy killing," and is understood to be the provision of an easy, painless death to one who suffers from an incurable or extremely painful affliction. Such an action is considered valid only when the suffering person wishes to die, or is no longer able to make such a decision.

A distinction is usually made between "active" and "passive" euthanasia. Active euthanasia occurs when actions are taken to produce death. This is often called "assisted suicide," as in the actions of Dr. Jack Kevorkian and others who have provided medical intervention which led directly to death. "Passive" euthanasia occurs when the patient is treated (or not treated) in a way which is intended to lead to death, but medical measures are not taken to cause death directly.

A third category has become common in recent years. "Letting die" signifies the decision to approach medical care so as to enhance the patient's well-being during the dying process. Unlike passive euthanasia, the doctor does not intend the patient to die as a result of this decision. Rather, the doctor withholds medical treatments which intensify suffering or merely postpone the moment of death for a short time.

For instance, it is not considered passive euthanasia to discontinue chemotherapy in cases of advanced cancer, especially if the drugs increase the suffering of the patient. The doctor does not intend this decision to cause death, even though death may result from his action.

In these terms, Terri Schiavo's death resulted from passive euthanasia, as physical sustenance was withdrawn for the purpose of ending her life. Food and water were not considered to heighten her suffering, as would chemotherapy. Their removal was intended to lead directly to her death.

The decision to enact passive euthanasia is termed "nonvoluntary" since Mrs. Schiavo could not express her wishes. However, her parents could call the decision "involuntary," believing that it went against her wishes as they believed she would have expressed them. Her death would have been "voluntary" if she had given "informed consent" while motivated by her own best interests (unlike a person suffering from mental or emotional illness who wishes to die).

If Mrs. Schiavo had executed a "durable power of attorney," she would have signed over all responsibility for her medical decisions to another person, usually her spouse. Because she did not take this action, the court gave her husband responsibility to make medical decisions for her, a decision known as "substituted judgment."

Maintaining Terri Schiavo's life would have required "heroic" or "extraordinary measures." Some patients wish only "ordinary means" which offer reasonable hope of benefit and are not excessively burdensome. A third means of support could be called "basic," providing only nutrition and water.

The doctors treating Mrs. Schiavo were required to help their patient ("beneficence") and to refrain from harming her ("nonmaleficence"). They could ethically provide medical assistance to alleviate any suffering, even if such help shortened her life. This "double effect principle" assures that doctors do not act immorally if they intend only the good effect, do not use bad as a means to good, and create good at least equal to the bad. For example, doctors can prescribe morphine to alleviate the suffering of a terminally ill patient, even if a side effect of morphine in that patient will shorten the person's life, unless they intend the drug to shorten or end that life.

Medicine has usually defined "death" to occur with irreversible cessation of circulatory and respiratory function, or with the irreversible cessation of the whole brain. But what is "brain death"? The "upper brain" supports consciousness, while the brain stem controls body functions such as breathing and heart rate. If the upper brain has died, the patient is considered to be in a "persistent vegetative state" (PVS). There are estimated to be 10,000 PVS patients in the United States. This was reported to be Mrs. Schiavo's condition.

If the brain stem has also died, the patient is considered to have suffered "brain death." Because nerve cells do not regenerate, upper-brain and brain death are completely irreversible.