Yong introduces the early 20th-century bio-philosopher Jakob von Uexkull’s theory of the umwelt, which roughly translates to “environment,” but which Uexkull uses much more specifically to refer to the “sensory bubble” each animal species inhabits. Yong claims that Uexkull’s theory of the umwelt is the guiding philosophy for his presentation of scientific research about animals’ senses. He aims to provide a glimpse of the amazing range of umwelten (the plural of umwelt) in the world.

“This is a book not about superiority but about diversity” (7), Yong insists, providing this array of information not so that humans can learn about themselves by way of animals but so that they can learn about different species within their umwelten while also recognizing that their own imaginations are limited by their umwelt. Because each animal’s umwelt is determined by its unique sensory adaptations, each species experiences the world “partially.” While people may be able to recognize that animals perceive their worlds differently than humans do and, thus, experience the world differently, people cannot inhabit animals’ umwelten or ever fully understand it.

Uexkull’s insistence that each species creates unique worlds of meaning through its sensory experiences guides Yong’s presentation of the senses across species lines. Thus, he also must contend with the seemingly simple question of how many senses there actually are.