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I sympathise with your leader concerning the reduction of meat-eating's environmental impact. If people can't be persuaded to reduce their consumption then anything we can do to improve its efficiency that isn't detrimental to animal welfare is welcome ( Leader, 2 March ). But the argument in the last paragraph, that it may be better …

Jenny Chapman makes some good points in focusing on nutrition, but why does any vegetarian food have to be ultra-processed? Caution over some margarines (those developed for profit more than for health) was warranted when the damage caused by trans fats came to light. Like most people I know, I will happily eat a veggie …

In comparing the complexity of the Crescent Nebula with the human brain, there may be a danger that we focus on the complexity of the structures, rather than the complexity of the outputs they produce. When evaluating the human brain in terms of output, it is hard to ignore the significance of consciousness. While this …

You ponder whether the human brain is the most complex object in the known universe. Without a brain there is no known universe, so the converse is more empirical: the universe is the most complex object in the human brain.

If we know that the skin is the largest organ of the human body, that it acts as a protective barrier to the ravages of our environment and is a first line of defence against infections, why do millions of people cover that organ daily with a range of chemicals and microplastics( 2 March, p …

Given the burgeoning awareness of various types of barrier protection provided by the skin, and the possibilities of assisting this in many ways, has there been no study into the impact that may be caused by tattoos? Indeed, might it be that what you put on your skin isn't as important as what you (don't) …

I agree with most of what Kirsty Sedgman wrote on how manners can be used to suppress others. As well as being mindful of the horrors of the past that she described, I'm old enough to remember having to sing the full version of All Things Bright and Beautiful at church and in school ( …

We have no solid basis for the common assumption that other people are conscious, let alone that a therapist feels with us and isn't merely emulating empathy.

Ruggeri clearly and correctly characterises empathy as "Ugh, I know exactly how you feel". She goes on to say that "ultimately, you can't really know what sadness is unless you have felt sad". There is the rub: a truly empathetic therapist, friend or confidant needs to have really been there. Where? Where no AI has …

You report that boiling tap water can remove microplastics. But this only really works for hard water, as the microplastics co-precipitate with the calcium carbonate. In which case, you must also avoid using the water in the very bottom of the kettle. I think I would prefer a water company to supply water without microplastics …