He parroted the now stock reply of any politician dealing with issues that involve science that his decisions will be "evidence-based". Does this mean that in other areas evidence does not matter? More seriously, what does "evidence-based" really mean? Evidence is collected according to hypotheses and then evaluated before a more conclusive proposal is made. (Yes, I know its not as tidy as this.) A different hypothesis may well result in different modes of evidence gathering. Even with the same mode, evidence is subject to interpretation. No evidence interprets itself. The same evidence is frequently interpreted in widely divergent ways.
In the abortion debate the main point of recent reference to evidence seems to involve the age at which the foetus can live outside the womb. This seems to me not to be a workable criterion or even a valid one. In practical terms it is likely that medical science will be able to push that age back even further than now. We know that a very early foetus can live for a time outside the womb during transplantation. The key issues are at what time does the foetus become a "person" with a right to life, and how do we define a "person". Is the prerequisite for becoming a "person" a certain level of consciousness? And what are the rights of that "person" with respect to the rights and wishes and health of the woman who is carrying the foetus. These are complex, slippery issues, and are ultimately ethical and emotional in nature. They cannot be decided by scientific evidence.
What is clear is that the visuals exploited by the anti-abortionists is often hugely rigged. This is an except from a piece I wrote in Nature some time ago (2005!). It was written in response to a two-hour
programme Life before Birth made in Britain by Pioneer Productions and directed by Toby McDonald.
The film was screened in Britain as In the Womb.
There were some glimpses of relatively raw scans, but most of the spectacular visuals relied on animated models made by Artemis. The foetuses were sculpted in wax, cast in silicon and hand painted. Animation specialists MillTV — better known for the creation of aliens in Doctor Who and for special-effects work in the film Gladiator — then set them in motion. The skill and imagination behind the models were of the highest order, and the results were seductive, visually and emotionally. We felt that we were eye witnesses to a beauty and conscious life previously unseen. But at no stage was it clear what we were seeing. The credits named the companies responsible, but didn’t explain how the images were generated, and they were all implicitly accorded the same level of “visual truth”.
Only on MillTV’s website is the process made clear: “After months of research, courtesy of 4D
ultrasound scans, medical books and pictures of mummified foetuses, MillTV developed anatomically
accurate CG recreations of month-four and month-seven foetuses.” Each elaborate and laborious animation involved such methods as “multilayering”for “shadowing, depth of field and colour correction flexibility”.
Where is the visual evidence here? Portraying something that cannot be "seen", other than by scanning with non-visible rays, involves high contrivance and deliberate choice. If we think that are four-month foetus has all the pink and pliable appeal of a Raphael bambino, our instinctive the attitude to the termination of its life is likely very different from only seeing an ultra-sound scan.
Not an easy issue. My stance is to support a woman's right to decide, given a balanced setting for that choice. But I really don't have "scientific evidence" for that stance.