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Ben Raskin of the Soil Association clearly exposes the problems of a failure to link agricultural production to the best nutritional outcomes (30 August, p 18) . The Sárpo potato cultivar that he lauds has been trialled by the UK Potato Council, but such blight-resistant varieties are not necessarily the potato of choice for processors …

Mary Midgley's review of Gary Greenberg's book The Noble Lie (13 September, p 46) addresses the important moral issue of the extent to which individuals are accountable for their actions, given that they may suffer from an addiction or mental illness, or environmental privations. Members of my own family have suffered from such afflictions: experience …

Contrary to Rachel Nowak's suggestion that in Australia "you can expect a reasonably comfortable end" (6 September, p 22) , many cancer sufferers here spend months in agony when permitted maximum doses of palliative drugs become ineffective. In Australia, unlike the UK, such distress is exacerbated by a legal prohibition on the clinical use of …

You reported how individuals who have consumed alcohol find other people more attractive, and the author expressed surprise that this also applies to people of the same sex (16 August, p 12) . It's just proof of the adage: "What's the difference between a straight man and a gay man? Four pints."

You may be interested in an additional way for the problem of the supply of organs for transplant (13 September, p 11) to be alleviated. I have tested my idea at www.deadbodyforsale.com – and been rewarded with the predictable responses that this is "unethical" and "ghoulish", with the establishment donor organisations telling the Melbourne Herald …

• We said that a musical instrument called an epigonion was introduced to Greece in AD 180 (13 September, p 23) but the accompanying caption suggested the instrument was played in 440 BC. To clarify: AD 183 is the earliest documented date for the instrument's existence; 440 BC is the date of the vase in …

Michael Bond's chart of the risks from different transport types gives food for thought (30 August, p 34) . The results are presented as deaths per billion passenger kilometres: this is most appropriate for comparing potential travel methods between fixed points. The apparent high risk of walking caught my attention. It raises questions about how …

You say a fuel consumption of 1.7 litres per 100 kilometres makes the ultimate "hypermiler" (20 September, p 26) . My 200-watt e-bike achieves 0.5 litres per 100 km equivalent in traffic and has a 30-kilometre range using one low-toxicity lithium-ion phosphate battery. It cost less than £1000, provides low-impact, stress-and-diabetes-reducing exercise, and does not …

Bijal Trivedi's article on the high carbon footprint of food (13 September, p 28) is a good illustration of the one of the problems caused by one particular farming system – modern intensive agriculture – but as her limited data from organic farming hints, to conclude that all farming systems have such high footprints would …

Jim Giles correctly identified one of the major hurdles to electric cars coming of age as the need to bring down the cost of the lithium-ion battery (20 September, p 26) . Another is the safety issue. The cell membranes in lithium-ion batteries currently in production are combustible organic polymers. If the car is involved …

• An editing error dropped a "not" from a letter by A Wills (online, 27 September) . The American Dental Association suggested in 2006 that fluoridated water should not be used to make up babies' bottle feeds.

James Humphreys queries (30 August, p 18) the distinction Lawrence Krauss draws between theism and atheism (2 August, p 52) when science makes suggestions about whether the universe has meaning. Surely it is not possible to demonstrate the nonexistence in reality of an imaginary concept, although a conjurer might try. It is not, then, the …

There is a real danger that trying to make sense of the complexity of calculating the greenhouse gas emissions associated with food (13 September, p 28) may lead to such unintended and environmentally damaging consequences as we have seen in the rush for biofuels reoccuring. For example, Bijal Trivedi says that the foods that produce …

If the Boeing 777 was indeed brought down at Heathrow by ice in its fuel (13 September, p 23) , it would not be the first. One night in 1948 or 1949 four Royal Navy Attacker FB2 aircraft "fell out of the sky" at Royal Naval Air Station Milltown in Aberdeenshire, UK. Each had almost …