Most AI during that time revolved around minimax, i.e, the chess move I play should be a response to the move you'd play if you were me, which is the move I'd p

Most AI during that time revolved around minimax, i.e, the chess move I play should be a response to the move you'd play if you were me, which is the move I'd play if I were you, etc. Lisp's inherent recursiveness lent itself to that theme.