death with dignity

A parishioner of mine said that he would never want to live as a “vegetable.” He wants to "die with dignity." Why should we keep people alive if they are unresponsive or just don't want to live any more? Shouldn't this be their choice?

To begin with, nobody should be referred to as a “vegetable.” We derive our dignity from being made in the image and likeness of God. Whether we are old or young, born or unborn, healthy or in a coma, we do not lose this most fundamental quality.
A “death with dignity” means different things to different people. All people desire a dignified death for themselves and for their loved ones. However, when a person's fear of death is exceeded by his fear of pain or loss of control, he is in a state of continuous mortal terror and may see death as a blessed release from his current situation. Such a person necessarily defines his degree of dignity by purely physical or emotional criteria.
By contrast, the Catholic Church perceives a loss of spiritual dignity when a person loses his focus on God and instead desires only a release from an existence that he or others may find pointless and wasteful.
True compassion demands that all of us love and support one another regardless of our functional capacity or appearance, and prepare the dying for their ultimate meeting with God. This is the true definition of living with dignity, even when in the last stages of dying.
Of course, severe pain suffered for too long can destroy the strongest of people. This is why the Catholic Church teaches that it is not proper to expect heroic virtue from all people, and that pain killers may be used, even if they lead to semi lucidity or quicker death in some cases (see Question 28 for elaboration on the licit use of pain killers).
A certain degree of pain at the end of life allows us to follow Christ all the way to the Cross. In one way, it seems inconsistent for Christians to be willing to suffer various indignities and inconveniences in the name of Christ over a period of decades during their lives, and then shy away from complete participation in the ultimate suffering of Our Lord at the point of death.
From a “slippery slope” point of view, euthanasia is much like other evils. We have seen in nations like Holland and the United States that it began with only the hardest of the hard cases, and now people who simply do not want to live are being euthanized, along with handicapped infants who have no say in whether they live or die. Our lives belong to God, and only He has the right to end them [Romans 14:7-8].1

1. See also the Catechism of the Catholic Church [¶2280]: "It is God Who remains the sovereign Master of life. We are obliged to accept life gratefully and preserve it for His honor and the salvation of our souls. We are stewards, not owners, of the life God has entrusted to us. It is not ours to dispose of.” Also see Congregation for the Doctrine of the Faith. Declaration on Euthanasia, May 5, 1980. The complete texts of the Catechism and the Declaration on Euthanasia are on Human Life International's Library Compact Disc.