Lewin coined the notion of genidentity,[7] which has gained some importance in various theories of space-time and related fields.[citation needed] He also proposed Herbert Blumer's interactionist perspective of 1937 as an alternative to the nature versus nurture debate. Lewin suggested that neither nature (inborn tendencies) nor nurture (how experiences in life shape individuals) alone can account for individuals' behavior and personalities, but rather that both nature and nurture interact to shape each person. This idea was presented in the form of Lewin's equation for behavior B = ƒ(P, E).