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Andrew Watson's article on food allergies was both enlightening and alarming (1 August, p 28) . Our daughter died about three years ago, aged 16, of anaphylaxis following ingestion of nut traces in chocolate. We had known about her allergy since she was a toddler, but the increasing incidence of the warning "may contain nut …

Hugh McLachlan argues that natural laws are by definition laws that cannot be transgressed – even by God (8 August, p 26) . He thus displays a defective understanding of what miracles in the Judaeo-Christian world are taken to be. The inhabitants of first-century Palestine understood perfectly well that all births required preceding sexual intercourse, …

Terence Kealey referred to a comprehensive analysis by the Organisation for Economic Co-operation and Development (OECD) of factors that might explain different growth rates of some of the world's leading economies (25 July, p 28) . This showed that only privately funded research and development led to economic growth, while publicly funded R&D did not. …

Is the pursuit of hypersonic flight the aviation industry's equivalent of controlled nuclear fusion (25 July, p 30) ? Even if sustained hypersonic flight powered by anything other than immensely wasteful rockets proves possible, it is unlikely ever to be practical. The Lockheed SR-71 "Blackbird" is the only Mach 3 plane ever built, for good …

Kate Douglas suggests that if people get a buzz from altruistic acts, they are not purely altruistic (8 August, p 28) . I can certainly attest to this. When cycling along a local street, I am occasionally accosted by people asking for small amounts of money. While I do not know if they are being …

If you place an even-money bet at roulette (red or black) will you inevitably win a small amount if you double your bet after every loss (8 August, p 35) ? No, for two reasons. First, casinos set betting limits on each table so if, for example, you have been doubling your bet after consecutive …

David Gilbert proposes that a disparity in the "vector relationship" between analysis and creativity explains the segregation of and alienation between the humanities and science (27 June, p 27) . It seems to me that the problem of "two cultures" (2 May, p 26) rather arises from the positivism of the French philosopher Auguste Comte, …

I cannot agree with Bryn Glover's rosy view of Star Trek as a socialist utopia (18 July, p 27) . The original series was about a warship and its crew, all dutifully obeying orders and Starfleet regulations. True, many stories did not involve military action, just as armed forces today also do humanitarian operations. We …

• The DOI for Steven Clapcote's paper on epileptic mice (8 August, p 14) is 10.1073/pnas.0904817106 . • The Planck length – the quantum of distance – is 1.6 × 10 -35 metres, not "about 10 -33 metres" (15 August, p 26) .