The early seventeenth-century French philosopher Rene Descartes believed that animals other than humans are insensate machines. Obviously, this was a restatement in rationalist terms of the Christian belief that only humans have souls. Even if mind and matter were categorically distinct, that would not mean humans alone have minds. It was reported that in order to test his theories, Descartes used to throw animals out of the window and observe their reactions. Looking at behaviour of this kind, one might reasonably conclude that humans are the senseless machines.

John Gray, in The Soul of the Marionette: a short enquiry into human freedom