In the beginning of his classic monograph, “A Stroll through the Worlds of Animals and Men” (1934/1957), the European naturalist Jakob von Uexkull invited his readers to “blow, in fancy, a soap bubble around each creature to represent its own world, filled with the perceptions it alone knows.… Through the bubble we see … the world as it appears to the animal (itself), not as it appears to us. This we may call the phenomenal world or the self world of the animal.” Von Uexkell then went on to suggest that for many biologists these worlds will be invisible because of a prior commitment to conceptualizing animal life in purely mechanical terms. He advises us, as enlightened readers, to regard all animals, the human being included, not as machinelike objects but as subjects who live in their unique worlds that are as “manifold as the animals themselves.”

Von Uexkull was not the only one of psychology's ancestors to call for a nonmechanistic and phenomenal view of human and animal life. A few years earlier, William James (1890) had written about the uniqueness of human perception, specifically in regard to four different Americans traveling in Europe: