Until recently there were only two certainties in life — death and taxes. Taxes were left to the politicians and death was left to providence or to fate. Now there is only one certainty, because death has become ambiguous, and besides we no longer leave it to providence.

Science and technology have made it easier to monitor — but much more difficult to understand or decide about — the process of dying, or even exactly what we define as the moment of death. Precisely because we know so much more, it has become more and more difficult to agree on when life has ended.

Equally, ideas have changed about when precisely life starts. There are those who are troubled by stem cell research at the microscopic beginning of life. Questions of life and death are no longer left entirely to deities or to experts; they are questions we now all ask, and more and more, people expect the right to decide the answers for themselves.

Many people will remember the very sad case of Diane Pretty in 2002, a terminally sick woman facing a very unpleasant death who longed for the right to be helped to die. She fought extremely bravely through the courts, ill though she was, and in the end she lost – both the legal battle and her life; she died as she had so much feared.

There were many people at the time, including me, who felt she should have been able to choose the moment of her death, probably through an overdose of anaesthetics, under very controlled circumstances, but necessarily with the assistance of a doctor or nurse. The law said no.

The law was wrong; the wishes of the individual should come first, particularly in a case like hers where all reasonable counter-arguments could be met. Besides, what she wanted is more or less what has happened up to now anyway, in many, many cases, but informally and therefore not as a legal right.

I can’t count the number of friends who have told me with great gratitude that their elderly mothers and fathers were gently eased out of life, and out of the great pain and distress of a terminal illness, by a good doctor who genuinely wanted the best for the patient and listened carefully to all concerned.

Upping the painkillers to lethal levels is in effect mercy killing, and if done with all due respect, it is truly merciful. Diane Pretty was wronged.

However, these things are never simple. There are hard cases the other way too, like the case in the High Court last week of Leslie Burke, a postman from Lancaster who is terminally ill with a degenerative disease.

His fear has been that at some point in the course of his disease, after he has become unable to move or speak, doctors will withdraw artificial nutrition and hydration (ANH), without which he would die.

Mr Burke does not wish medical people to decide upon the hour of his death; he doesn’t want ANH to be withdrawn at all.

On Friday he won his battle; the High Court ruling on his case has now made it significantly more difficult for doctors to withdraw life-sustaining treatment from seriously ill patients.

Until Friday, doctors had discretionary powers to withdraw such treatment, depending on their judgment about a patient’s quality of life. But naturally enough it is possible that a patient who could not speak or move might have a different view from the doctor’s about his quality of life.