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Agency alone isn't enough for free will. A self-driving car has a sophisticated form of agency, but no free will. What is needed for free will is creative agency: the capacity of an agent to create its own goals and means for pursuing them ( 30 September, p 32 ). These are created when they …

Debating free will, or the lack of it, by reference to neuroscience is a category error. Neuroscience is a scientific discipline; free will is a philosophical, moral and religious concept. Brains make decisions and there is no ghost in the machine.

In the article "Risk of mass deaths in heatwaves", you describe the threat to humans of exceeding the maximum survivable wet-bulb temperature and mention that this can be mitigated by, for instance, being in a cool building ( 16 September, p 8 ). But there is no mention of other species. Animals and plants must …

You reviewed Raymond Hickey's book Life and Language Beyond Earth , mentioning his prediction that aliens will be humanoid, based on a need for locomotion and manipulation. This reminds me of author Larry Niven's argument that most extraterrestrials will be bipeds that traced their ancestry to a fish-like being that emerged from the sea and …

Lucy Foulkes discusses possible downsides of "the language of vulnerability and victimhood and harm" creeping into everyday life, saying this could actually make us feel worse. I was reminded of 1997 research on the impact of certain stereotypes on performance ( 23 September, p 33 ). In this case, college women did just as well …

Of course the whole brain is used in language. The human brain, the most complicated structure in the known universe, evolved. Had it been designed, we might find nice separate compartments for language, motion, thought and so on. But evolution is utterly opportunistic. Any genetic mutation that increased our capacity for language, even a little …

In his call to rethink how climate policy is communicated to policy-makers, Sharpe fails to mention the integrated assessment models (IAMs) that have underpinned Intergovernmental Panel on Climate Change reporting to governments for three decades. These are technology focused and highly dynamic. They track the unit cost of existing technologies against uptake, assess speculative technologies …

Concern over China's carbon emissions misses a key point. In the 1950s, when vehicle use was really beginning to take off, British models were made from steel produced domestically and from locally mined iron ore and coal ( 7 October, p 12 ). Now, the same car could be made from ore and coal mined …

Your fascinating article about deciphering historical documents written in code made me wonder where the code-breaking sources that must have been needed by the senders and recipients of these documents are ( 23 September, p 40 ). Have none been found? No worksheets where recipients struggled to "translate" what they were given? Are there no …

Thank you for putting aside the hyperbolic, catchy factoids on the gut microbiome to give clear comment. There are trillions of residents in our colons, but we are still in the very early stages of defining which microbial make-ups are better or worse ( 7 October, p 30 ). Greater microbial diversity appears to be …