PRINCETON – Throughout his tenure as South Africa’s president, Thabo Mbeki rejected the scientific consensus that AIDS is caused by a virus, HIV, and that antiretroviral drugs can save the lives of people who test positive for it. Instead, he embraced the views of a small group of dissident scientists who suggested other causes for AIDS.

Mbeki stubbornly continued to embrace this position even as the evidence against it became overwhelming. When anyone – even Nelson Mandela, the heroic resistance fighter against apartheid who became South Africa’s first black president – publicly questioned Mbeki’s views, Mbeki’s supporters viciously denounced them.

While Botswana and Namibia, South Africa’s neighbors, provided anti-retrovirals to the majority of its citizens infected by HIV, South Africa under Mbeki failed to do so. A team of Harvard University researchers has now investigated the consequences of this policy.

Using conservative assumptions, it estimates that, had South Africa’s government provided the appropriate drugs, both to AIDS patients and to pregnant women who were at risk of infecting their babies, it would have prevented 365,000 premature deaths.

That number is a revealing indication of the staggering costs that can arise when science is rejected or ignored.  It is roughly comparable to the loss of life from the genocide in Darfur, and less than half of the toll from the massacre of Tutsis in Rwanda in 1994.

One of the key incidents in turning world opinion against South Africa’s apartheid regime was the 1961 Sharpeville massacre, in which police fired on a crowd of black protesters, killing 69 and wounding many more.

Mbeki, like Mandela, was active in the struggle against apartheid. Yet the Harvard study shows that he is responsible for the deaths of 5,000 times as many black South Africans as the white South African police who fired on the crowd at Sharpeville.

How are we to assess a man like that?

In Mbeki’s defense, it can be said that he did not intend to kill anyone. He appears to have genuinely believed – and perhaps still believes – that anti-retrovirals are toxic. We can also grant that Mbeki was not motivated by malice against those suffering from AIDS.

He had no desire to harm them, and for that reason, we should judge his character differently from those who do set out to harm others, whether from hatred or to further their own interests. But good intentions are not enough, especially when the stakes are so high.

Mbeki is culpable, not for having initially entertained a view held by a tiny minority of scientists, but for having clung to this view without allowing it to be tested in fair and open debate among experts.

When Professor Malegapuru Makgoba, South Africa’s leading black immunologist, warned that the president’s policies would make South Africa a laughingstock in the world of science, Mbeki’s office accused him of defending racist Western ideas.

Since Mbeki’s ouster in September, the new South African government of Kgalema Motlanthe has moved quickly to implement effective measures against AIDS.

Mbeki’s health minister, who notoriously suggested that AIDS could be cured by the use of garlic, lemon juice, and beetroot, was promptly fired.

The tragedy is that the African National Congress, South Africa’s dominant political party, was so much in thrall to Mbeki that he was not deposed many years ago.

The lessons of this story are applicable wherever science is ignored in the formulation of public policy. This does not mean that a majority of scientists is always right.

The history of science clearly shows the contrary. Scientists are human and can be mistaken. They, like other humans, can be influenced by a herd mentality, and a fear of being marginalized.

The culpable failure, especially when lives are at stake, is not to disagree with scientists, but to reject science as a method of inquiry. 

Mbeki must have known that, if his unorthodox views about the cause of AIDS and the efficacy of anti-retrovirals were wrong, his policy would lead to a large number of unnecessary deaths.

That knowledge put him under the strongest obligation to allow all the evidence to be fairly presented and examined without fear or favor. Because he did not do this, Mbeki cannot escape responsibility for hundreds of thousands of deaths.

Whether we are individuals, corporate heads, or government leaders, there are many areas in which we cannot know what we ought to do without assessing a body of scientific evidence. The more responsibility we hold, the more tragic the consequences of making the wrong decision are likely to be.

Indeed, when we contemplate the possible consequences of climate change caused by human activities, the number of human lives that could be lost by the wrong decision dwarfs the number lost in South Africa.

Peter Singer is Professor of bioethics at Princeton University. His next book, The Life You Can Save: Acting Now to End World Poverty, will be published in March.