The game of Go, which originated before 500 BC and perhaps as early as 2300 BC, is a case where particularly simple rules manage to allow remarkably complex patterns of play to occur. … Some of Leonardo da Vinci 's planned book on "Geometrical Play" from the early 1500s has, however, survived, and shows elaborate patterns satisfying particular constraints.

And when early efforts to make computers perform tasks such as playing games were fairly successful, the expectation developed that general human-like thinking was not far away.

In the variational approach to gravity mentioned above, the RicciScalar plays the role of a Lagrangian density for pure gravity—and in the presence of matter the Lagrangian density for matter must be added to it.