The Highest Possible Level of Development civilization. A gravely injured hermit comes to Trurl's house and tells Trurl of Klapaucius's adventure: Klapaucius wanders across an old robot, who tells him that he has logically deduced the existence of a civilization that reached the highest possible level of development (hence "HPLD"). He has inferred the existence of such a civilization by figuring that if there are different stages of development, there will be one that is the highest. He was then faced with a problem of identifying that one; as he noted, everyone claimed that theirs was the HPLD.