Friday Night Theology

The Miracle of Green Blood

15 June 2007

Science fiction became fact this week when the medical journal The Lancet reported the unusual case of a man with green blood. The doctors could not quite believe their eyes when they operated on him, but due to the prescription drugs he was taking, there it was: "dark green blood in the operating theatre".

This is not the first reported case of a patient with green blood, but nevertheless green blood remains an extremely rare phenomenon. The medical literature has only a handful of such cases, which raises the important question: Why do we believe these stories?

The first answer is that we believe them because they come from a reputable source: the authors are all established doctors, and the journal is well respected. However, all the journal editors and us, as readers, have to go on is the eye-witness accounts of those doctors.

And if you think about it, this is pretty flimsy evidence given the claim that is being made. After all, every time I have ever seen blood it has been of the traditional red variety. And I suspect that if I asked everyone I knew if they had ever seen green blood, they would say no. We also know that scientists (including doctors) very occasionally exaggerate or even fabricate their findings just to get published in prestigious journals.

Why, then, do we believe this story- despite its remarkable claims and the possibility of fabrication?

We believe it because of what is called the 'principle of credulity'. This principle states that we should adopt a basic attitude of trust or belief, until we are given sufficient reasons to disbelieve. The important point is that merely being able to think up possible reasons why someone might lie is not a good enough reason to doubt. Rather, we should doubt only when in fact we have positive reasons to disbelieve -perhaps because of contradictory evidence, or a previous track record of lies.

We see this principle at work in science every time a scientist relies upon their instruments, or the expertise of other scientists, or the results of other scientists' experiments. This point, though, seems to be lost on a certain brand of atheist who thinks that the principle of faith inherent in Christianity is at odds with the scientific method. This is simply not the case. In Christianity, we rely on the testimony of others in just the same way that scientists rely on each other's work.

So, if our sources are reliable, then we should trust what is being said however remarkable the claim. This applies just as much to New Testament accounts of the resurrection, as it does to Lancet tales of green blood. If our friends are willing to believe the green blood story, then it is inconsistent and irrational for them to dismiss the narrative of what God has done - either in the pages of the Bible, or in our own experience of him.

Justin Thacker, Head of Theology