Probability does not exist, claims Cambridge professor

On BBC Radio 4's More or Less on 30 December 2011 Professor David Spiegelhalter, Winton Professor of the Public Understanding of Risk at Cambridge University announced, 'Probability does not exist' .

He defines probability in the programme as 'reasonable betting odds that we construct on the basis of our knowledge and understanding'. But he emphasises that we cannot use probability to tell us, for example,  an individual's risk of developing certain illnesses. Probability as we understand it depends on our knowledge of the situation: we can't rely on it without assuming that we have perfect knowledge.

This supports our view that so-called 'science' based on passive smoking is quite unscientific. If we can't tell a person his or her risk of heart disease, we cannot tell either how much it will be elevated by smoking, drinking, being exposed to smoke or whatever the current fad is. An individual's risk of all these things is also affected by their environmental exposure to risk factors for heart disease, their genetic make-up and other issues that cannot be calculated scientifically.

As far as I understand probability it's a mathematical concept, where the parameters for the different probabilities are known, as they are in the problems presented here. When you can't be sure about the parameters, the probability concept doesn't really work. This applies for much of what is said about smoking as Frank Davis discusses here, and the same applies to any single factor such as consumption of alcohol or junk food (even the definition of junk food is problematic). I once heard of a young woman who had all the symptoms of cervical cancer but was refused screening on the grounds that she was unlikely to have it on the grounds of her age. Here is a case where the low probability of breast cancer in men resulted in the denial of treatment to a man who had (100 per cent probability of) breast cancer.

Professor Spiegelhalter will take his ideas further at this event (evening/smart dress recommended).