“I could go on. A professor at Berkeley, Philip Tetlock, has looked at tens of thousands of predictions made by hundreds of experts over a period of ten years, and reached the conclusion that the accuracy of such predictions would have been the same if they’d been randomly generated by a computer.

“There are situations in which making predictions is unavoidable. The awareness of how unreliable they are should, however, lead us to be cautious – whatever our profession, because in every profession we make judgement calls and gamble, often unconsciously, on their outcome – in order to thwart the enemy number one of good judgement: fallacies, errors made in the formulation of an argument that render it invalid or incorrect.”

I went on to say that fallacies prevent a discussion – whether public or private – from advancing logically and in fact make exchanges of opinion pointless and judgements invalid or incorrect. I covered this subject at some length, and after a while realized I had to get to the point if I wanted to keep to the time limit.

“There are many kinds of fallacies, and we don’t have time today to linger over the various categories, which are something cognitive scientists and exponents of argumentation 123theory deal with. Anyone who wants to go into the subject in greater depth – which I would strongly recommend – will find some excellent works on the market, some of them educational.

“Right now I’d like to use as a springboard the observation that what we say is often invalidated by procedural errors in the examination of the facts. Strictly speaking, what we mean by incorrect procedures are those characterized by infractions of the rules regarding due dates, time limits, filing of suits. But procedures that lead to fallacious arguments, whether or not those who perpetrate them are aware of it, are also incorrect procedures, because they infringe the rules on valid discourse.

“The function of the defence counsel is to make sure that nobody is convicted on the basis of incorrect procedures, and this function can be summed up as what we might call ‘the act of asking questions while doubting’. Asking questions, of others but above all of ourselves, doubting accepted truths and rules. In each sphere – rules and facts – as an exercise of our intellectual and ethical muscles. Taking nothing for granted.

“Was the killing of Osama bin Laden a premeditated murder or a significant act of justice, a form of pre-emptive self-defence, given that the man might be planning further criminal acts? The same could be asked of the killing of Palestinian terrorists by the Israeli secret service. And is it legitimate to torture a terrorist to make them reveal the whereabouts of a hostage whose life is in danger or the location of a deadly device that’s about to blow up and kill innocent people?