"I was involved in a cloning project. .. to send me into outer space along with a lot of other people. Not the whole me - just a hair from my head, while I still had some. I would thus pop up in another galaxy in the distant future."
- Arthur C. Clarke

The history of tests to distinguish human beings from machines is short, but interesting. Alan Turing devised what is commonly known as the Turing Test; the crux of the test is language usage.

It is intriguing to note that Dick has vacated the field from the standpoint of trying to defend human intelligence versus machine intelligence; he relies on emotional response. Biometric data are also used to authenticate the person being tested. At the time the novel was written, computers were able to play chess, but poorly. (Turing himself wrote the first chess program in 1950, using a limited size board and fewer pieces. Claude Shannon published the first article on the subject, outlining how a computer would evaluate and choose positions. Chess programs reached Grand Master status by 1988.)