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Consciousness is, and always has been, a territory littered with shape-shifting concepts. Your article ( 23 June, p 28 ) illustrates this. Consciousness is acknowledged to be an " emergent " property of more fundamental processes: so the discussion is like trying to define the shape of smoke – a major problem is where to …

The wager between David Chalmers and Christof Koch on finding a specific signature of consciousness in the brain by 2023, as described by Per Snaprud , was over before it began. The entire endeavour of searching for neural correlates of consciousness is predicated on a reductionist methodological assumption that rules out in advance the very …

Did anyone think human evolution was a linear series? It's a marvellous rat's nest. Marjorie Meldrum responds to our report of bizarre fossils from China rewriting the story of human evolution ( 7 July, p 28 )

You are concerned by biological bias in clinical trials (Leader, 30 June ). In the late 1980s, I was studying for a master's degree in public health. We were told even then that women were excluded from many clinical trials because of "hormone fluctuation". I had two questions: if drugs are not tested on women …

Clare Wilson reports research on a variant of the "trolley problem", in which people were told they could save five mice from an electric shock by choosing to inflict pain on one ( 19 May, p 14 ). I don't recall anyone addressing why people presume they have a right, let alone are obligated, to …

Your articles on "How to think about..." were all fascinating. But the piece on the multiverse claimed that it is not a hypothesis but is "forced upon us" ( 30 June, p 29 ). There is no evidence for a multiverse. It seems very much like the idea that the sun revolves around Earth: it …

Daniel Cossins discusses two kinds of multiverse : inflationary and quantum. Both seem to assume that everything started with our one solitary big bang. That seems parochial, akin to this Earth being unique and at the centre of all things. Is it not more conceivable that many big bangs have created many universes? Or, indeed, …

• Divers get the bends when they ascend ( 30 June, p 41 ). • Strewth! Australia occupies less than one-ninth of Earth's circumference at its latitude, but aerials there can "see" one-third of a satellite's orbit ( 30 June, p 25 ).

You report that wearing a tie restricts blood flow to the brain ( 14 July, p 20 ). This confirms my long-held view that I don't think better when wearing a tie, so I refuse to wear one. You have also reported online ( 24 May 2004 ) that half of doctors' ties carry disease-causing …

Roger Taylor mentions that to battle the absence of reason in government, there is a need for engaging the public (Letters, 23 June ). I suggest posters in issues of Â鶹´«Ã½ , detailing – with diagrams, pictures and graphs – the most pressing issue reported that week. Readers could display these publicly.