The inquest into the death of Princess Diana is drawing to a close, and the coroner Lord Justice Scott Baker has been summing up to help the jury to reach a verdict. Among other things, he has advised them on the credibility of one of the witnesses at the inquest, Diana’s butler Paul Burrell.

The BBC summarised his comments about Burrell like this:

Lord Baker suggested to the jury that Mr Burrell may have given evidence while thinking that “whatever he said might have an impact on his future enterprises”. Mr Burrell worked for Diana from 1992 and described himself as “Diana’s rock” - but Lord Baker said he was “quite a porous rock” given that many of the princess’ secrets were made public. The coroner said: “I advise you to proceed with caution especially if you are left with the impression that he only told you what he wanted you to hear. “On the other hand he was close to Diana and was particularly well-placed to hear information that others were not. The fact that he has not told you the truth on some occasions does not mean you cannot accept anything he he has told you. But you should proceed with caution.”

[Source: BBC News: Diana's butler 'obviously' lying]

In other words, although Burrell, being close to Diana, has a good ability to see, his vested interest to advance his own career means that he can’t be relied on.

How far would you stretch the truth to impress people?

A chef from Swindon faces losing his US cooking show after it was discovered that he had lied about his achievements. His desire to promote himself to open up career opportunities seems to have got the better of him.

Robert Irvine claimed to have made part of Charles and Diana’s wedding cake, and to have prepared meals for Presidents, despite having only picked fruit for the cake and worked in the White House mess. He also claimed to have a Knighthood, and that the Queen had given him a Scottish castle as a present, both of which Buckingham Palace dispute.

Irvine had not only worked on Dinner: Impossible, but had also written a book to accompany the show and lent his name to a “Royal Titanium” cookware range (which some vendors are now withdrawing from sale).

Irvine is far from alone in getting a career boost from half-truths, however; reportedly, one in four people lie on their CVs. Vested interest can affect us all.

A recent poll has shown that the public continue to support women having the right to choose to have an abortion. The poll was commissioned by Bpas, a charity that provides around 50,000 abortions each year, and conducted by Mori. 63% of those asked agreed with the statement, “If a woman wants an abortion, she should not have to continue with her pregnancy.” Bpas have reportedly cited the data collected as a reason to liberalise current abortion legislation.

There is always a concern with surveys commissioned by a group with a clear vested interest, such as this one: the way that the questions were framed might have distorted the results. Interestingly, some of the questions in this poll were varied, making it possible to see this phenomenon in action.

Half of those polled were asked about their attitude towards the current law which allows abortion up to 24 weeks with the consent of two doctors. The other half were asked about their attitude towards the current law which allows abortion up to 24 weeks but were not told about the requirement for doctors’ consent. 54% of the first group agreed with the current law, while 28% opposed it; 46% of the second group agreed with the current law, while 38% opposed it. This serves to illustrate how much difference the way that questions are framed can make.

The conclusion drawn from the data by Bpas is also of interest. If their argument were that the public endorsement of abortion implies that there is nothing wrong with it (call this “the moral argument”), then it would clearly commit the appeal to popularity fallacy. The moral status of an action and public opinion towards it are two different matters. If the majority of the population backed racial discrimination, for example, then that wouldn’t make it right.

If, on the other hand, Bpas’s argument is not to do with the moral status of abortion but with the legal status of abortion (call this “the legal argument”), then they may be on more solid ground. The argument, “The public backs abortion on demand, therefore the government should permit abortion on demand”, need not be understood as drawing a conclusion about whether abortion is morally right or wrong. Instead, it could be understood as drawing a conclusion about how the government should legislate.

Why is the second argument better than the first? Because it rests on a more plausible assumption.

The moral argument, in inferring the conclusion “There is nothing wrong with abortion” from the reason “Most people believe that there is nothing wrong with abortion”, makes an assumption: “Whatever most people believe is the case.” This assumption, however, is often false; often the majority opinion is incorrect. This is why appeals to popularity are fallacious.

The assumption made by the legal argument is slightly different. The legal argument infers the conclusion “The government should permit abortion on demand” from the reason “Most people want the government to permit abortion on demand.” The assumption made by this argument is that the government ought to do whatever most people want the government to do. This assumption is not obviously true–we can imagine situations in which following public opinion would lead to catastrophe–but it is more defensible than that made by the moral argument. In a democratic system, where the government is elected to rule for the people, the legal argument might just fly.

One thing that this shows is the importance of clarifying precisely what an argument is before it can be assessed. Several different conclusions are attributed to Bpas in several different places: e.g. that abortion should be available on demand, that the current legislation should be relaxed, and that it is time for the government to review abortion legislation. The stronger the conclusion they draw from the data, the weaker their argument gets.