“Cogito ergo sum – I think, therefore I am – was coined by René Descartes in 1637…. [His maxim] turns out to be of the most famous examples of recursion, the process of embedding ideas within ideas that humans seem to do so effortlessly. So effortlessly and so skilfully, in fact, that it’s beginning to look like the one true dividing line between animals and humans that may hold up to close scrutiny.”