  The most influential figure in logical AI is John McCarthy. McCarthy was one of the founders of AI, and consistently advocated a research methodology that uses logical techniques to formalize the reasoning problems that AI needs to solve. All but the most recent work in McCarthy’s research program can be found in  Lifschitz 1990a,  which also contains an introduction to McCarthy’s work  Lifschitz 1990b;  for additional historical background, see  Israel 1991.