Of all the arguments against voluntary euthanasia, the most influential is the slippery slope: once we allow doctors to kill patients, we will not be able to limit the killing to those who want to die.

When fish experience something that would cause other animals physical pain, they behave in ways suggestive of pain, and the change in behaviour may last several hours.

There are many cases in which gifted children have done great things without special school programs. There are also gifted kids who have been to special schools and achieved nothing that has benefited the world as a whole. Without solid evidence, I have no confidence that funding school programs for the intellectually gifted would do more good than the most cost-effective programs to help people in extreme poverty.

My view is different from this, only to the extent that if a decision is taken, by the parents and doctors, that it is better that a baby should die, I believe it should be possible to carry out that decision, not only by withholding or withdrawing life-support - which can lead to the baby dying slowly from dehydration or from an infection - but also by taking active steps to end the baby's life swiftly and humanely.

We should aim for our children to be good people, and to live ethical lives that manifest concern for others as well as for themselves.

Should one break in and free the animals? That is illegal, but the obligation to obey the law is not absolute. It was justifiably broken by those who helped runaway slaves in the American South, to mention only one possible parallel.

We may feel the pain of falling back from a level of affluence to which we have grown accustomed, but most people in developed countries are still, by historical standards, extraordinarily well off.