Richard Dawkins, the world's most famous atheist, loves a headline. He got plenty recently when he tweeted that it is immoral not to abort a baby with Down Syndrome if you have the choice.

In response to the fury and outrage, he half-apologised, claiming he was merely following the logic and that most people aborted babies with Down Syndrome.

He explained that;

if your morality is based, as mine is, on a desire to increase the sum of happiness and reduce suffering, the decision to deliberately give birth to a Down baby when you have the choice to abort it early in the pregnancy, might actually be immoral from the point of view of the child's own welfare.

Lay aside, for a moment, the preposterous ideas that someone's welfare is improved if they are not allowed to exist, or that people with Down Syndrome cannot lead rewarding lives and bring pleasure to others.

The problem with fundamentalists ­whether Christian, Muslim, secularist, nationalist, communist, economic rationalist — is that they believe there is only one right way, and they will tell you what it is. Defined that way, Dawkins, who says bringing up children to believe in God is child abuse, is an atheist fundamentalist.

One thing fundamentalists often say is that they are "merely following the logic". History shows how often "merely following logic" leads to evil.

The Americans who sterilised tens of thousands of hillbillies and other despised groups from the 1920s were merely following the logic of the idea "these people shouldn't have children". The Nazis who murdered nearly 300,000 disabled people, were merely following the logic of the idea "these people are a burden and don't deserve to live". Both claimed to be acting in accord with science, which simply shows that science cannot determine morals. That is not its role.

Here's something Dawkins would know if he did not despise philosophy and theology as irrelevant: logic is a tool. It's not an end in itself, it's an aid to reasoning. If the premises are invalid, the logic will be unsound. And that is what has happened here.

I do not suggest Dawkins is a Nazi or anything like it. I do suggest he has a warped sense of morality. He agrees that people can love someone with Down Syndrome, but says this is emotion, not logic.

In morals, emotion is not necessarily a bad thing. In fact most of us know very well that the noblest morals are seldom logical. We generally agree that the highest and most enriching value is love (which Down Syndrome people can give and receive as well as anyone).

Love's highest expression, in compassion, mercy and self-sacrifice, is almost never logical as in self-advantageous. Some mothers replied to Dawkins that their Down Syndrome children live fulfilling lives and bring joy into the lives of those they meet through their zest, affection and openness to others, and I know this personally.

In other words, such people are not always and only a burden to parents and society, as Dawkins implies. But ­and this point is vital — they don't deserve life on the grounds that they can smile, but because they are human beings, as are people with more serious disabilities, who perhaps cannot smile.

Here I disagree with Dawkins about how we should understand human life. Christians believe, as he obviously does not, that all humans are made in the image of God, and therefore possess unconditional value and dignity. Yes, the disabled too.

This understanding about the equality and value of life, which has helped shape Western civilisation and is enshrined in the Universal Declaration of Human Rights, is in fact far from universal. Many cultures and religions have not thought this way. And now in the West this foundational view is slipping, as Christian values slowly recede. They are being replaced by the fake ethical system of utilitarianism, which Dawkins says is what guides him.

It also guides Australian philosopher Peter Singer who advocates infanticide if a baby — logically, even a healthy one is inconvenient, on the grounds that it does not have the consciousness that gives life meaning. The parents' happiness has increased while the baby has lost nothing it valued because it is not yet capable of such preferences. Logical? Perhaps. Wicked? Entirely.