91É«ÇéƬ

At the end of your very interesting exploration of "the self" ( 23 February, p 32 ) you slip into the dichotomy of subjective illusion and objective reality, with the self in the first category. I suggest it is more profitable to remember that objects, from our bodies to quantum dualities, are also constructed by …

In his account of the optical illusion known as the beta phenomenon (23 February, p 34) , Jan Westerhoff rules out the hypothesis that our brain constructs the image we experience after it has received all the data. He concludes that "there is not enough time for a delay of sufficient length to explain the …

In your self special (23 February, p 32 ) you wrote: "Some thinkers even go as far as claiming that there is no such thing as the self." They think, therefore they are not? I'm reluctant to heed the opinions of a nobody. Surely the greatest trick the mind has played is to convince people …

In his letter, Peter Ryan suggested tackling carbon emissions by making the consumer pay via a direct tax on goods (22/29 December 2012, p 41) . However, like all logical and fair systems there is a downside. Presumably there will be a commission to determine the CAT (carbon added tax) and an appeals tribunal to …

Fifteen researchers who have worked with the Yanomamö Indians for long periods during the past five decades wish to respond to Daniel L. Everett's review of Napoleon Chagnon's book Noble Savages (2 February, p 44) . All consider the Yanomamö to be generally peaceable. As many traditional people do, they occasionally engage in inter-village conflicts, …

Paul Marks calls aluminium alloy in aircraft "tried-and-trusted." Tried? Yes, and revealed as a treacherous material whose strength can be destroyed by a little crack. If a crack in a stressed section has grown too long it will race across the alloy, snapping it in two. The more heavily and often aluminium is loaded, the …

Further to your interview with Brian Hare on the importance of dog domestication to our own evolution (2 March, p 30) . We know that human lifestyles changed from hunter-gatherer to pastoralism. This was a crucial step in human cultural evolution. The practical possibility, and hence probability, of the advent of pastoralism must have increased …

As an organic farmer, I have long argued that we should "close the loop" and return sewage to the land, as advocated in your look at the use of human waste (16 February, p 48) . In the 1980s, such a scheme was promoted in the UK, and we were poised to use treated sludge …

If you were a Neanderthal being hounded by humans, what time would you have for child's play, burial ceremonies or art (23 February, p 28) ? To verify this you might compare creative pursuits in the UK during the last war and, say, 10 years later.

It is interesting that the immune system can be primed to fight off infections that have chemical similarities to those it has already encountered (16 February, p 16) . But does it mean that some people may have been misdiagnosed with chronic diseases such as HIV and hepatitis C because they appear to have antibodies …

In your article on Amazon's plan to enable the sale of second-hand MP3s and ebooks (23 February, p 22) you state that US company ReDigi is selling second-hand e-music, and that "software checks the seller does not retain a copy". I understand how it can check for copies in online and cloud-based storage, or even …

• Theories of reality don't measure up, and neither did our decimal places. We should have said the average density of baryonic or "ordinary" matter in the universe of 0.426 yoctograms per cubic metre equates to 0.25 protons per cubic metre (2 March, p 40) . • Our opinion piece on water grabbing (2 March, …