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Former UK government adviser Simon Sharpe is dismissive of carbon taxes as a means of tackling the climate crisis, instead urging investment "in new technologies and new systems" ( 30 September, p 37 ). But these aren't mutually exclusive. He himself says that we need "investment in targeted subsidies so that these solutions can take …

I agree that new AIs have shortcomings. When I asked ChatGPT to write a story in the style of Agatha Christie, it wrote pages of frighteningly realistic text until it broke the most basic rule of crime writing: it told me that it was the gardener who did it ( 7 October, p 20 ). …

You report on a study that predicts nearly all mammals will go extinct in 250 million years as continents recombine and the climate shifts ( 30 September, p 9 ). However, I assume that the changes will occur so slowly as to allow considerable time for evolution. Humans may be long gone, but, as a …

Researcher Alexander Farnsworth anticipates that, due to natural processes, atmospheric carbon dioxide will reach levels incompatible with mammalian survival in a quarter of a billion years. He hopes that "we'd be a space-faring civilisation by that point". But the technical challenges in managing atmospheric CO 2 levels are trivial compared with those of human interplanetary …

I offer further arguments against the existence of free will. First of all, two of the greatest minds to have ever lived, Bertrand Russell and Albert Einstein, scoffed at the very existence of free will ( 30 September, p 32 ). Secondly, many parents of more than one child will attest to how different their …

Are the forces of evolution so powerful and compelling that they negate free will? Or are they so powerful and compelling that they create free will? Either you have no choice or you have no choice but to have choice.

Brian Kateman argues that lab-grown meat firms should focus on staple foods before they produce versions of exotic meats. In this way, we can increase public acceptance of cultured foods and reduce the adverse impacts of animal farming ( 14 October, p 21 ). Surely the effort involved in persuading people to eat lab-grown chicken …

Claims made about our gut microbiome and health greatly exceed the causal evidence. It is telling that the European Food Standards Agency hasn't, to date, approved any health claims for probiotics, foods or supplements that intentionally contain live bacteria. Its decisions are based on the sum of evidence reviewed by independent experts – clearly, they …

Having read James Wong's take on native versus non-native plants, I agree that more research on this is needed, but I wish he hadn't attributed a preference for native plants solely to "cultural bias". In fact, there are good reasons to think that native plants will tend to be better ( 30 September, p 44 …

Guy Cox can't see civilisation surviving 6 to 9 metres of sea level rise. It can. Most land and many great cities are higher than that, so we would still have plenty of room. In any case, it would take centuries for the sea to rise that much, and most buildings don't last that long …