Sir, most people in orthodontic and dental practice will be aware of Dr Mew's beliefs (BDJ 2005; 199: 495–497) and I have resisted responding to them in the past to avoid adding fuel to the fire. I feel however I have to respond to his latest article in the BDJ, not on the grounds of the comments he makes about orthodontic practice but his misuse and obvious misunderstanding of the concepts of empiricism.

A central concept in the philosophy of science is empiricism, or dependence on evidence. Empiricism is the view that knowledge is derived from our experience throughout our lives. In this sense, scientific statements are subject to and derived from experiences or observations. Scientific hypotheses are developed and tested through empirical methods consisting of observations and experiments. Empiricism therefore has been a cornerstone of all science from the Enlightenment to the modern day and is the process whereby theories are tested and science advanced. In the medical and dental sciences this would be part of the concept of evidence-based practice.

Just because the current evidence refutes Dr Mew's claims of growth guidance does not mean he can dismiss it as not being science. In fact the reverse is true. His views that are based on deductive logic are the ones that fail to stand up to the objective rigours of empirical investigation. The problem with any form of logical argument is that it has to be based on assumptions or premises that are true. Dr Mew's premise is that the cause of malocclusion is environmental or more specifically poor oral posture. He therefore argues that if oral posture is corrected malocclusion can be cured. However, the aetiology of malocclusion is poorly understood and all we can say at this stageis that it is certainly multifactorial. Therefore his premise is based on personal opinion and is certainly not a scientific truth. As such the whole of his argument is far less scientific than the empiricism of current research evidence that he constantly decries.

Francis Bacon, one of the great empiricists, who set the stage for modern science, warned us to be wary of the 'idols of the mind' and teachings based solely on words and personal opinion. As before the burden of proof remains with Dr Mew, and in future if he is going to use big words to try and impress us he should really understand what they mean.