It is time to talk of last things. There are currently two poignant photographs in the news: that of Leslie Burke, a 45-year-old with a degenerative brain condition, and already in a wheelchair. We know about him because he has just been putting his case to three appeal court judges. The other picture is that of Abigail Witchalls, paralysed in a hospital bed but smiling at her son who, in the arms of his father, is reaching out to her. One is of someone who is seeking to have control over his own impending death; the other of someone slowly growing back to the life so brutally threatened by a criminal attack on her and her child. What is at question in both is the power of speech: how do we communicate with the world when we can't use words?

Unless we are run over or jump from a bridge, it is likely that towards the final hours or even days we will lose the power of speech. I have sat at the bedside of the dying and I know the problems at first hand. How are thoughts and wishes to be conveyed? You feel suddenly helpless to know what they want.

Imagine how they must feel, with a brain fully active and striving to make contact, but slowly drifting away for ever, and at the mercy of others to decide things for you. It is at that moment you may well wish you had talked things through earlier - as Burke is trying to do now, and about something quite specific. He wants it made clear that whenever he is "no longer competent" the doctors will not have the right to deny him food and water. He is saying now, while he can, that he doesn't want them to do that.

He is right to get things sorted out before it is too late. I have sat beside someone I loved and seen how the failing breath dries out the mouth, and leaves the tongue parched. I have helped with regular sponging, to make it possible for them to gasp a few words. I have watched nurses hold a patient's hand and insistently ask them to "squeeze once for 'yes' and twice for 'no'." The dying of the light brings the inevitable fading of the voice. We need to be ready for its going.

The problem is, no one wants to talk about it. Death? Leave that until later! I broached the subject with my family once and was kindly reassured that we can get round to that when the time comes. But surely it might by then be almost too late. If we want some say in our own deaths, we need to speak up now, or we risk being starved to death.

The arguments are already in the courts, which means it is virtually too late. People we don't know are already discussing what might or might not be "in the patient's best interest". The British Medical Association, speaking for the doctors, is arguing that a patient does not have the right to insist on any particular form of treatment. But a landmark ruling made last year in Burke's favour means that doctors must provide treatment - ANH, or artificial nutrition and hydration - even though the doctor believes "the treatment will provide the patient with no clinical benefit or will be futile". Is keeping someone artificially alive a clinical benefit or not? And is it our right? If so it is not a very appealing one.

Medical ethics are in a tangle. If it is a doctor's duty to persist in keeping us alive when we have a serious heart attack, massive injuries or untreatable cancer, then it is surely their duty, having landed us in this state, to give us an acceptable death. How do we know what the withdrawal of nourishment feels like? Sadly, there is no answer, because the patient can't tick the boxes. The dead don't come back to tell us how bad a long and lingering starvation was compared with an extra shot of morphine, or perhaps a mercy-killing pillow. Even those conjured up in darkened rooms by mediums usually confine their comments to criticising the new wallpaper or sending their love to Auntie Flo. If only one of them would say: "Look, taking away that food and water was really agony. For heaven's sake, when it's her turn, give Auntie Flo a shot of something lethal. Cutting off food and water is a medical cop out."

Then we might have something to go on. It would almost be worth believing in spiritualism.