Thoughts within thoughts make us human

[David Morris]

http://www.newscientist.com/blogs/culturelab/2011/06/thoughts-within-thoughts-make-us-human.html

Cogito ergo sum - I think, therefore I am - was coined by René
Descartes in 1637. He was struggling to find a solid philosophical
basis for how we know about reality and truth.

This is also 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.

That's the hope of Michael Corballis, professor emeritus of psychology
at the University of Auckland, New Zealand. His new book, The
Recursive Mind: The origins of human language, thought, and
civilization, is a fascinating and well-grounded exposition of the
nature and power of recursion.