There is magnificent irony in Chris Ormell's article "Putting reality back into the equation" (20 January) when he declares that "Mathematics tends to be...misunderstood", as his own profound misunderstanding of it is evident in every paragraph.
All mathematics is of the form: if certain hypotheses hold, certain conclusions must follow. Therefore, in applying mathematics, you must always verify that the hypotheses hold, or the conclusions are invalid.
Ormell blames the financial crash on "blind faith" in mathematics. My experience of the way non-mathematicians treat mathematics leads me to believe that it was a refusal on the part of senior managers to engage with even the most elementary part of the mathematics, namely verification of the hypotheses, that fostered disaster.
It is common in statistical models to treat sources of randomness as independent, because not doing so makes things vastly more complicated. But it is a matter of everyday experience that individuals and institutions do not behave independently: at a certain point the herd instinct takes over. Therefore, these statistical models, which were in common use, are valid only up to that point.
It is part of the senior manager's job to know which tools to use and when. In the financial crisis, failure to understand that the necessary condition of statistical independence no longer applied was a failure of management, not of mathematics.
When Ormell says that "we have misread the relationship between mathematics and the real world", he is talking only about himself. Real mathematicians have a real understanding of this relationship.
Robert Wilson, Professor of pure mathematics, Queen Mary, University of London.