[T]he philosopher Carl Cohen writes:
We incorporate the different moral standing of different species into our overall moral views; we think it reasonable to put earthworms on fishhooks but not cats; we think it reasonable to eat the flesh of cows but not the flesh of humans. The realization of the sharply different moral standing of different species we internalize… In the conduct of our day to day lives, we are constantly making decisions and acting on these moral differences among species. When we think clearly and judge fairly, we are all speciesists, of course. (Cohen, 62)
I would first note that Cohen is using the term "speciesist" incorrectly, since he is talking not about the importance of "species" but about the importance of qualities that are correlated with our perceptions of species. His argument is therefore irrelevant because it ignores Singer’s point that individuals of different species (and individuals of the same species) should be treated differently insofar as they have morally relevant differences- just as men have no right to an affordable mammogram and wealthy white men have no right to the benefits of affirmative action. But what I really want to draw attention to is the question, what does Cohen mean by "species"? One might think that it would be giving Cohen the benefit of the doubt to just name one, preferably one that is accepted by many experts. Let's suppose, for instance, he is talking about Mayr’s biological species concept, which defines a species as a group of individuals capable of interbreeding and producing fertile offspring. But surely Cohen does not believe that when we "are constantly making decisions and acting on these moral differences among species,” we are making our decisions based upon matters of who is capable of breeding with whom. For, not only do we not need to know any information about the mating capabilities of these animals to make moral distinctions between them; most of us wouldn’t even know what to do with this kind of information if we had it!
So perhaps Cohen means a "commonsense" concept of species. That is, what is morally relevant are the distinctions that we are all capable of making simply by looking, with no scientific or philosophical training. What is morally relevant, in other words, is appearance. Yet I doubt that when Cohen wrote this passage he had appearance in mind as a morally relevant characteristic. For Cohen, unlike Darwin, the difference between humans and other animals is not merely one of degree, but one of kind. It is difficult to imagine how Cohen might hold this essential difference of kind to be based upon appearance. More likely, he would probably claim that we make distinctions between species based upon appearance, but it is not the appearance that is morally relevant but something else that is inevitably correlated with appearance. For instance, we distinguish between worms and cats based upon how they look, but the morally important distinction is ‘something else’ that is correlated by appearance.
But unless someone can tell us what this ‘something else’ is, it is only prudent to assume that it is a "vivid illusion,” as biologists Frank Keil and Daniel Richardson argue in "Species, Stuff, and Patterns of Causation" (Keil and Richardson in Species, 273). And remember, this ‘something else’ cannot be intelligence, self-awareness, language, or capacity for suffering, because then those properties would be the morally relevant characteristics- but no one argues that they are equivalent to "species.” This ‘something else’ must simultaneously satisfy at least two conditions, which I believe is impossible. First, it must correspond with what we really mean when we talk about species, and second, it must at least be plausible that it is really the basis of our moral distinctions between supposed species. Mayr’s biological species concept and species concepts based on genes or DNA, for instance, do not satisfy the second condition. And properties like rationality and language do not satisfy the first condition.
In other words, my main reason for saying that species is socially constructed is that we often unconsciously argue as if species has an essence; as if there is something about species in the background that can not be described, but which can simultaneously satisfy both the first and second condition. Given the basis of any species concept, few would argue that that basis is morally relevant in any significant way. Given the basis of Mayr’s biological species concept, few would argue that whom we have the ability to mate with is a relevant characteristic for determining how much moral consideration we should be granted (Lewis Petrinovich may be an exception, though his work is not altogether clear on the matter). Given the major basis of commonsense notions of species, few would argue that how we look should determine how much moral consideration we should be granted. Why, then, do some philosophers hold that our species can determine how much moral consideration we should be granted? I believe it is because they do not equate species with any biological or commonsense way of determining species. Rather, they are probably committing Washoe’s fallacy, thinking of species membership as some essential characteristic of an individual that, in reality, does not exist.