The question of the relation of sex to gender, and how each of these things are even defined in the first place, has become hotly disputed with the recent Caitlyn Jenner controversy. It is therefore timely to articulate the subtle, underlying philosophical disputes regarding the concept of the “natural kind.” To speak of a “natural kind” is to say that it corresponds to something which exists objectively in nature rather than being a social fiction. The relevance to the controversy is obvious: Does having sex reassignment surgery, and identifying as a male or female, regardless of one’s biological sex at birth, mean that one has changed one’s gender or sex? Is sexual difference, if it exists at all, discrete or is it continuous? That is, is one either man or a woman, or is sexual identity more fluid and continuous.
It is important for the scientific realist to consider objects of scientific inquiry natural kinds rather than social conventions. The realist wants his taxonomies sand classifications to correspond to what is observed in nature. It ought to be understood, however, that to speak of a “natural kind” does not exclude substances which are artificially produced or synthetic. Thus, “natural” does not mean “occurring in nature without human assistance.” Instead, it simply responds to objective items in the world.
The concept of the natural kind is relevant to both epistemology and metaphysics. For example, new objects, such as new microorganisms, may require changes in our current biological taxonomies. Likewise, phlogisticated air was once regarded as a natural kind prior to Lavoisier’s chemical revolution. If elements of societies are to be regarded as natural kinds, likewise, they may change as societies rise, develop and fall.
According to the naturalist advocate of weak realism, there are ways of grouping or classifying things that are natural. To group a pig with a quark is not a natural grouping, whereas grouping metals together is natural. Other classifications, such as cars made in Japan, are not classifications of natural kinds because they are invented to serve human interests. Some classifications are therefore natural kinds and some are not. This view is called “naturalism.” It is widely regarded as an essential component of scientific realism. These realists hold that scientific theories represent phenomena that exist independently of humans. Likewise, the classifications of the periodic table represent objective natural divisions between the elements. This realism may also be associated with other forms of realism, such as realism about universals.
For the naturalist, it is not necessarily the case that everything humans instinctively think are natural, are in fact, natural. For example, reptiles are no longer considered a natural kind, although they once were considered natural kinds by biologists. Nevertheless, this does not discourage naturalists. They insist that there are indeed natural kinds, and it is the job of the scientist to discover them. For the naturalist, members of a natural kind must have at least some natural properties in common. Though a necessary condition, it is not sufficient. Objects which are of totally different kinds may possess properties in common, but there may be little or no other overlap in their kindhood. As J.S. Mill famously said, white objects do not constitute a natural kind despite this similarity.
Natural properties are often seen as possessing intrinsic properties. This leads to problems when it comes to biological kinds, as will be seen later on. Some argue that not all natural properties are intrinsic. According to J.S. Mill and Quine, natural kinds must be able to permit inductive inferences. This is not alone sufficient to distinguish objects sharing a natural property from those who do not. Natural kinds must also participate in laws of nature, according to some. If something is a turtle, then it has webbed feet. But the believer in natural kinds would not consider this a law of nature, at least not in the same way as he would Newton’s law of gravitation. Therefore, even though this may be a necessary condition, it is not a sufficient conditions.
Next, natural kinds, for the naturalist, must overlap one another in some way. The Linnaean taxonomy in biology provides examples of this. Organisms of different species may be members of the same genus, and, therefore, all members of both species are embers of that genus. Finally, natural kinds must be categorically distinct. The distinction between the two must be discrete rather than continuous. For example, there must be sharp lines dividing chlorine and argon, both of which have a distinct number of protons. There is no midpoint between the two; these chemicals, though neighbors in the periodic table, are totally and irreconcilably unique and separate from one another.
Opposed to naturalism is the doctrine of conventionalism. According to this position, also known as constructivism or constructionism, natural kinds do not exist independently of scientists. These scientists call them into existence and invest into them certain meanings. The conventionalist thus denies that any classifications, even those of t he scientist, are natural kinds. Instead, categories are constructed out of human interests. There is a difference, however, between weak conventionalism and strong conventionalism. For the weak conventionalist, classifications are very unlikely to be natural. These people are skeptical about the possibility that science can discover natural principles of classification. John Locke was an example of a weak conventionalist. Skeptical though he was about the objective existence of conventions, he nonetheless entertained the possibility that there might be microstructural essences which distinguished species from one another, although he was skeptical about the ability of scientists to discover or observe them.
For the strong conventionalist, however, there is no such thing as a natural kind. The idea of a natural kind is purely a social construct. Thus, Caitlyn Jenner, according to a strong conventionalist, is not doing anything that is objectively abnormal, since “male” and “female” are totally arbitrary conventions which serve human interests. In this case, they are seen as having special political and social interest. They hold this even of chemicals in the periodic table, and affirm that there is nothing outside the realm of discourse. Hacking refers to this as universal constructivism, and he argues that some constructed categories do indeed reflect real divisions. In any case, it is the essential contention of the conventionalist that to speak of a “fact” is to speak of something dependent upon, and created by, a human being.
This article will continue explorations of the concepts of sex and gender. Recall that in the previous article, the question was broached concerning whether or not sex and gender are natural kinds, or if they are merely social constructions. Some people think that sexual differentiation is metaphysically objective, whereas others regard it merely as a social construction. In other words, are sex and gender “natural kinds,” or are they merely social conventions? This has crucial implications for how individuals conceive of their identities.
Dupré argues for what he refers to as a “promiscuous realism.” According to this, there are an infinite number of potential ways of classifying the world. How the world is carved up has entirely to do with the sorts of interests we have. This is not a conventionalist view, he argues, but is most emphatically a naturalist and realist account of natural kinds. While natural kinds have certain properties in common, these are not “intrinsic” kinds. Furthermore, he believes that there is a hierarchical structure of natural kinds, and that different kinds can be categorically distinct from one another.
An example of two distinct ways of carving up the world would be the distinction between ‘common sense’ classification as opposed to scientific classification. “Lilium,” for example, consists of over 100 species of flowers, whereas “lily” in common usage does not refer to plants belonging to the lilium genus. He uses this as an example of the sort of pluralism possible in classification. Both are legitimate, and both function to reveal the sort of interests the individual has. He also believes that biological classification in terms of species reveals a wealth possible means of classification, each of which may reflect objective realities.
For the realist, as noted before, natural kinds objectively exist. Naturalism is sometimes regarded as synonymous with “weak realism,” so the term “strong realism” may be used strictly for the idea that metaphysical natural divisions exist.
The realism/nominalism debate which plagued the medieval West, and persists with us today. Must a class of entity, universals, be postulated in order to account for properties? The nominalist may affirm that individuals may be spoken of, but deny that there is an entity which can be classified, but will deny that there entities apart from each individual thing. For the strong realist, however, we cannot explain the distinction between natural and non-natural classifications within invoking the concept of the natural kind.
A distinction must be drawn between natural classification and natural kinds. Conventionalism and naturalism are positions on natural classifications, whereas realism and nominalism refer to natural kinds. One may believe in natural classifications without believing in natural kinds. The realist believes in natural kinds. Naturalists, on the other hand, may believe in natural groupings or distinctions, but such a person does not necessarily believe that these natural groupings or classifications are metaphysical natural kinds. That is, naturalism does not commit one to a metaphysical commitment. He does not necessarily believe that there is a metaphysical category called a “natural kind.” The realist, on the other hand, does believe in a metaphysically distinct kind of entity known as a “natural kind.” As noted before, “Weak realism” may refer to a bare naturalism, according to which one accepts natural classifications, whereas strong realism may refer to belief in both natural classifications and natural kinds. Such a person insists that there is a discrete boundary between, for example, lead and silver, as two different kinds of metals.
The philosopher W.O. Quine advocated a form of natural classifications. He believed that kinds are sets and that entities belonging to sets are kinds. In this respect, he is a realist. Sets are ubiquitous, however, so he was a minimalist in his realism. Quine argued that similarity and kinds are basically the same thing, and that relative similarity ought to be defined such that a is more similar to be than to c if and only if a and be share more properties than a and c do. For Quine, the existence of natural kinds is crucially bound up with what tends to confirm induction. He argues that it is similarity or sameness between events which allows induction to take place. Some suggest that humans have evolved, or are in some respect, neurobiologically predisposed to, carve nature into joints in which some natural kinds are given special attention. While Quine believed in natural classification to a degree, he believed that science would eventually help us to get rid of the concept of the natural kind, and focus on ever more particular and singular components of entities, thus liberating us from illusory and superficially similarities.
Some realists advocate what has come to be known as cluster kind realism. According to this position, the members of a natural kind have a common natural set of contingently clustered properties. These properties may cluster together because of an underlying internal mechanism or extrinsic contextual mechanism which secures their co-occurrence. Thus, the critical realism concerning sex and gender discussed in earlier articles in this series, would be similar to cluster kind realism, since such realism speaks of overwhelmingly strong tendencies, rather than the presence of one or two properties that are shared by absolutely all members of a natural kind. None of the properties, for the cluster kind realist, are individually necessary for counting a member as a member of a kind, and certain pressures may affect and alter the set of properties with such and such a kind or such and such a member of a kind, of course:
“Boyd considers biological species to be paradigmatic natural kind clusters (1999), where the clustering is due to a homeostatic mechanism. Homeostatic property clusters occur when mechanisms exist that cause the properties to cluster by ensuring that deviations from the cluster have a low chance of persisting; the presence of some of the properties in the cluster favours the presence of the others. A homeostatic mechanism thereby achieves self-regulation, maintaining a stable range of properties. In the case of species, the homeostatic mechanisms may be intrinsic (e.g. gene exchange within a population or developmental factors) or extrinsic (e.g. a species’s evolutionary niche provides common selective factors). Since individuals inherit their basic characteristics from their parents, and very few people are taller than 2.5m, we can expect the next generation to contain few people of that height. Height can, however, be affected by environmental factors; a mutation can cause offpring to have genes different from their parents that might cause greater than usual height, and malfunctioning of the pituitary gland can cause an excess of growth hormone. So there can be individual cases of excessive height. But they will remain rare because such gigantism and acromegaly are accompanied by serious complicating disorders and often result in premature death. Consequently, these individuals are less likely to reproduce than others. Even greater extremes of height (e.g. 4m) are just not possible, since the same developmental factors would prevent the individual from being viable at an earlier stage in life.”