The following passage is from a discussion of various ways that living creatures have been classified over the years. The world can be classified in different ways, depending on one's interests and principles of clas- sification. The classifications (also known as Line taxonomies) in turn determine which comparisons 5 seem natural or unnatural, which literal or analog- ical. For example, it has been common to classify living creatures into three distinct groups—plants, animals, and humans. According to this classifica- tion, human beings are not a special kind of 10 animal, nor animals a special kind of plant. Thus any comparisons between the three groups are strictly analogical. Reasoning from inheritance in garden peas to inheritance in fruit flies, and from these two species to inheritance in human beings, 15 is sheer poetic metaphor. Another mode of classifying living creatures is commonly attributed to Aristotle. Instead of treat- ing plants, animals, and humans as distinct groups, they are nested. All living creatures 20 possess a vegetative soul that enables them to grow and metabolize. Of these, some also have a sensory soul that enables them to sense their envi- ronments and move. One species also has a rational soul that is capable of true understanding. 25 Thus, human beings are a special sort of animal, and animals are a special sort of plant. Given this classification, reasoning from human beings to all other species with respect to the attributes of the vegetative soul is legitimate, reasoning from 30 human beings to other animals with respect to the attributes of the sensory soul is also legitimate, but reasoning from the rational characteristics of the human species to any other species is merely analogical. According to both classifications, the 35 human species is unique. In the first, it has a king- dom all to itself; in the second, it stands at the pinnacle of the taxonomic hierarchy. Homo sapiens is unique. All species are. But this sort of uniqueness is not enough for many 40 (probably most) people, philosophers included. For some reason, it is very important that the species to which we belong be uniquely unique. It is of utmost importance that the human species be insulated from all other species with respect to 45 how we explain certain qualities. Human beings clearly are capable of developing and learning languages. For some reason, it is very important that the waggle dance performed by bees * not count as a genuine language. I have never been 50 able to understand why. I happen to think that the waggle dance differs from human languages to such a degree that little is gained by terming them both "languages," but even if "language" is so defined that the waggle dance slips in, bees still 55 remain bees. It is equally important to some that no other species use tools. No matter how inge- nious other species get in the manipulation of objects in their environment, it is absolutely essential that nothing they do count as "tool use." 60 I, however, fail to see what difference it makes whether any of these devices such as probes and anvils, etc. are really tools. All the species involved remain distinct biological species no matter what decisions are made. Similar observa- 65 tions hold for rationality and anything a computer might do. According to the author, what is most responsible for influencing our perception of a comparison between species?
