APA Dictionary of Psychology

the notion that new scientific theories do not gain acceptance by a systematic process of validation that convinces opponents of their truth. Instead, as opponents of a new theory grow old and die, they are replaced by a new generation of scientists, who were exposed to the theory early in their careers and have come to accept it. This notion is a direct challenge to both verification and falsificationism. [Max Planck (1858–1947), German physicist]