In this paper, I defend the view that law is a social kind, which is to say that it is a natural kind in the social domain (compare: tiger is a natural kind in the biological domain). I will base my argument on a naturalist conception of natural kind that I have defended in earlier work. According to this “simple causal theory” of natural kinds, a natural kind is a node in a causal network and such causal networks are attested in the social domain as well as in the natural domain. Having defended the claim that law is a social kind, I will go on to make two sets of distinctions among social kinds. The first distinguishes kinds based on whether they are causal, etiological (or historical), and copied. I will argue that law is an etiological kind, but not a copied kind (though other legal kinds would seem to be copied kinds). The second distinction has to do with the ways in which social kinds can be mind-dependent, namely whether they are merely mind-dependent, or whether they are additionally concept-dependent. I will argue that law (like many other legal kinds) is such that it is not only mind-dependent but also concept-dependent.
What would it take for law to be a social kind? I will defend the view that a social kind is nothing but a natural kind in the social domain (just as, say, a biological kind is a natural kind in the biological domain). Then, armed with a particular conception of natural kinds, I will go on to set forth the conditions that law and other legal kinds would have to meet to be social kinds. While some legal kinds may not be social kinds in this sense, I will put forward some defeasible reasons for thinking that law itself is a social kind. I will then go on to make two sets of distinctions among social kinds. The first distinguishes kinds based on whether they are causal, etiological (or historical), and copied. I will argue that law is an etiological kind, but not a copied kind (though other legal kinds would seem to be copied kinds). The second distinction has to do with the ways in which social kinds can be mind-dependent, namely whether they are merely mind-dependent, or whether they are additionally concept-dependent. Law and many other legal kinds are such that they are not only mind-dependent but also conceptdependent. I will also ask whether law and other legal kinds are such that each token is concept-dependent or whether only the type is concept-dependent. I will conclude by considering the implications that these features of law and legal kinds have for their standing as social kinds.
Although it may sound oxymoronic to talk about natural kinds in the social domain, I
believe that this is a misconception for two reasons. The first is that according to the
originators of the expression, “natural kind” was not supposed to apply exclusively to
the domain of the natural sciences. John Venn, who seems to have been the first to use
the term “natural kind” (cf. [
different Kinds, or logical species, of man. The various races and temperaments, the two sexes, and even the various ages, may be 1 Corresponding author. Copyright © 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
differences of kind, within our meaning of the term. I do not say that
they are so. [
The second, and more substantive, reason that it is justified to posit natural kinds in the social domain relates to the particular account of natural kinds that I will defend in this paper. According to that account, as I will explain in the following section, natural kinds are nodes in causal networks, and I will argue that those networks can be found in the social domain just as much as in other domains. Before doing so, it is worth elaborating in a little more detail Mill’s view of kinds since it serves as the starting point for so many others.
Mill’s own account of kinds is not always easy to decipher and presents problems of interpretation. I will begin by explaining the more straightforward aspects of his view, then progress to those that are more contentious. Mill thinks that chemical elements, chemical compounds, and biological species (as well as some higher taxa) are paradigmatic examples of real kinds. Furthermore, he holds that they are distinguished by the fact that members of these kinds share an inexhaustible number of properties in common.
Some classes have little or nothing in common to characterize them by,
except precisely what is connoted by the name: white things, for example,
are not distinguished by any common properties except whiteness; or if
they are, it is only by such as are in some way dependent on, or connected
with, whiteness. But a hundred generations have not exhausted the
common properties of animals or of plants, of sulphur or of phosphorus;
nor do we suppose them to be exhaustible, but proceed to new
observations and experiments, in the full confidence of discovering new
properties which were by no means implied in those we previously knew.
[
Another puzzling feature of Mill’s account is that he sometimes indicates that the
properties of real kinds should not be linked as causes to effects. Rather, it seems that in
his view, the inexhaustible number of properties associated with each natural kind should
simply be unrelated, whether causally or logically. For instance, he claims that if a
property (e.g. blackness in crows) is not the “effect of causation” (presumably of other
properties of crows), then it is a property of the kind crow, but if not then it would not
seem to be a distinguishing property of the kind [
In some cases, a Kind is sufficiently identified by some one remarkable
property: but most commonly several are required; each property
considered singly, being a joint property of that and of other Kinds. The
color and brightness of the diamond are common to it with the paste from
which false diamonds are made; its octohedral form is common to it with
alum, and magnetic iron ore; but the color and brightness and the form
together, identify its Kind: that is, are a mark to us that it is combustible;
that when burned it produces carbonic acid; that it can not be cut with
any known substance; together with many other ascertained properties,
and the fact that there exist an indefinite number still unascertained. [
There is a growing tendency to do metaphysics, and ontology in particular, by taking our
cue from science. I would argue that this tendency is, in fact, more in line with the attitude
of the nineteenth century authors mentioned in the previous section, who were effectively
providing an ontological basis for science. Accordingly, if we are interested in
identifying natural kinds, we should pay attention to the way in which the scientific
enterprise determines which categories correspond to genuine groupings in nature. This
attitude applies (or should apply) to the social sciences no less than the natural sciences.
Thus, the naturalist project in metaphysics advises us to pursue social ontology by paying
attention to the deliverances of the social sciences (see e.g. [
There are various implications of this attitude for social ontology. One such implication is that in talking about putative candidates for social kinds we should restrict ourselves to ones that could conceivably play a role in social scientific theorizing, as we do when we talk about natural kinds. In the natural domain, we don’t usually focus on categories such as bushes, clouds, and sand, but rather such categories as gold, water, and tiger. Similarly, in discussing social ontology we should avoid categories such as professor, basketball team, and book club, and instead direct our attention to such categories as: consumer, corporation, and political party. From this perspective, law and other legal kinds can be considered as social phenomena that interact with other social phenomena, such as systems of government and economic markets.2 The laws that a society passes obviously influence the kinds of political structures and activities that emerge, as well as the economic transactions and institutions that take place. The influences here are broadly causal in nature, as when we say that a carbon tax law encouraged companies to reduce carbon emissions, or the absence of corporations in Islamic law hindered economic development in the Islamic world, or that a strong democratic system of government requires the rule of law. Law and other legal phenomena are here considered as causal structures in the social world that causally influence, and are influenced by, other social phenomena. These causal structures consist of various types of social phenomena: individuals, institutions, events, processes, and others, interacting causally with one another. Like many other social phenomena, law and particular laws (e.g. laws governing contracts, or freedom of expression) play a causal role in the social domain. In this respect, they are analogous to entities and other phenomena in the biological, geological, meteorological, or epidemiological realms.
Which of these phenomena correspond to real or natural kinds? According to several
recent naturalist account of natural kinds, which are supposed to apply to the social and
natural domains alike, kinds are grounded in causality (e.g. [
When it comes to both natural and social kinds, one can make an important distinction between those that are individuated intrinsically, or according to their synchronic causal powers, and those that are individuated etiologically, or according to their diachronic causal history. Both synchronic and diachronic kinds may be natural kinds, according to the causal conception of natural kinds outlined in the previous section. One can think of synchronic natural kinds as initial nodes in causal networks, causal properties that generate a number of other causal properties in turn. Meanwhile, diachronic natural kinds can be conceived of as terminal nodes in causal networks, properties that are the regular effects of a chain of other causal properties. One way of characterizing etiological kinds in general terms is as follows:
history, or causal trajectory.
This characterization immediately gives rise to a distinction between those kinds whose members share a token history and those whose members share the same type of origin, history, or causal trajectory.
Token-etiological kinds have members that all originate in the very same event, or have followed the same token causal trajectory, or share the selfsame history. One of the most extensively discussed cases of this type is that of biological species. According to a widely accepted view of the nature of species, members of a biological species are classified together because they are all descended from the same set of common ancestors. Consequently, they have the same token origin and share the same token history. A common history is, of course, not the only thing that members of a species typically share, since for many species, the ability to interbreed and produce fertile offspring is widely held to be criterial for species membership. Members of a given species also often have many intrinsic features in common, so biological species are what might be called “impure” or “hybrid” etiological kinds, since they share more than just a history. This observation gives rise to another distinction, that between pure etiological kinds, whose members share nothing but an origin or history, and hybrid etiological kinds, whose members may share intrinsic features too, and may be classified into kinds based on both etiological and intrinsic features.
As for type-etiological kinds, they do not share the very same token origin or history but rather the same type of origin or history. Their members do not originate in the same event or follow the very same causal pathway, but their origins or histories are tokens of the same type. For example, in geology, igneous rocks do not all originate from the same source but they are created by the same type of process, namely the solidification and crystallization of hot magma or lava. This is a repeatable process in the history of the earth (and perhaps other planets) and has occurred a multitude of times, each time producing rocks with the same type of origin and causal history. Igneous rocks are classified as such on the basis of the process that led to their formation rather than their intrinsic or synchronic properties.
So far, I have contrasted etiological kinds with kinds that are individuated on the basis
of intrinsic properties. But it is worth pointing out that etiological kinds are not the only
extrinsic kinds, since functional kinds are also extrinsically or relationally individuated
but synchronically rather than diachronically. Hence, etiological kinds are individuated
both extrinsically and diachronically, by contrast with many paradigmatic natural kinds,
which are individuated on the basis of intrinsic and synchronic features.
To gain further insight into the nature of etiological kinds, it will be useful to look briefly
at a couple of preceding discussions. Perhaps one of the earliest attempts to discuss
classification on historical grounds, can be found in William Whewell’s Philosophy of
the Inductive Sciences [
Since Whewell’s seminal treatment, philosophers do not appear to have paid the topic
of etiological kinds in general much heed, though there has been renewed interest in
recent years in the historical sciences and historical explanation. Perhaps the most
explicit treatment of etiological kinds in the recent philosophical literature occurs in
Millikan ([
It is instructive to look at law and other legal kinds through the lens of this distinction. It seems safe to say that law is an etiological kind, since whether something is a law has a great deal to do with its origin. Law as an institution and individual laws must arise in the right way in a society and have a certain provenance. A rule, norm, or custom could not be considered a law unless it had the right causal history. Having said that, it may be hard to say what exactly that provenance has to be; in particular, it might not have to be a result of explicit legislation by a representative body. However, it would seem as though there are clear focal instances, as when a piece of legislation is enacted by an elected body of representatives or adopted as a result of a popular referendum. There are also clear non-instances, as when a certain society has prevalent rules of behavior or etiquette that are enforced by what Mill calls the “magical influence of custom.” The former are typically regarded as laws, while the latter would not ordinarily be regarded as laws. But law is likely to be a hybrid etiological kind, like species, since it does not appear sufficient for it to have arisen in the right way. It also needs to have the right synchronic functional properties. For example, unless there are some mechanisms of adjudication and enforcement, a law or system of laws is unlikely to be regarded as such. Since law has clearly arisen numerous times independently in various human societies, it is a type- rather than a token-etiological kind. Some legal kinds, however, may be token-etiological kinds. Certain legal doctrines, such as habeas corpus, and institutions, such as parliament, may have this character. That is because they may not be considered instances of the relevant kind unless they are descended from the very same origin. Moreover, these token-etiological legal kinds can also be considered copied kinds, in Millikan’s sense, since they are all copied from each other or from a common template.3
Another useful distinction to be made among natural kinds is one between minddependent and mind-independent kinds. It would seem as though most, if not all, social kinds are mind-dependent since they depend for their existence on the existence of minds and mental activity. Among mind-dependent kinds, one can also distinguish those that are concept-dependent from those that are not. This gives rise to a three-fold distinction, as I will try to explain. First, there are social kinds whose nature is such that human beings need not have any propositional attitudes towards them for them to exist (e.g. recession, racism). The existence of these kinds clearly depends on the existence of human beings and depends on those humans having certain propositional attitudes. There can only be racism in a society if some members of that society are prejudiced against others or harbor attitudes of superiority or contempt towards them insofar as they are members of a different group. But members of that society need not have any propositional attitudes that involve the concept racism itself. They may never have consciously formulated such a category or concept; indeed, the racists may be in denial that they have such attitudes and the victims of racism may never have articulated the concept. Nevertheless, certain human propositional attitudes must clearly be in place for racism to exist. Therefore, such kinds are mind-dependent but they are not conceptdependent.
The second kind of social kind includes those whose existence is at least partly dependent on specific attitudes that human beings have towards them. In other words, some members of society need to have the concept of the kind in order for the kind itself to exist. This would seem to be true of social kinds like money or war. In these cases, at least some members of society need to have propositional attitudes involving these categories themselves for those kinds to exist. For money to exist, we need to have a practice and attitudes that incorporate the category money. Where there is currency in various denominations, there is surely a set of rules or conventions, whether explicit or implicit, and the introduction of such conventions requires having thoughts involving the category itself.
The third kind of social kind includes those whose existence and that of their instances are both dependent on attitudes that human beings have towards them. These kinds are not just concept-dependent; every instance of the kind is itself conceptdependent. In this case, not only must some members of a society have attitudes towards the kind itself, each individual token of the kind can only be such if it has been considered to be such by some members of society. To illustrate, no one could be a permanent resident of a certain jurisdiction without being recognized as such by at least one government official. In other words, the concept must be applied to each individual member of the kind. Similarly, a corporation could not be a corporation without being explicitly conceptualized as one, at least by the owners or shareholders. In these cases, not only does the kind as a whole need to be recognized under the relevant concept, each instance of the kind needs to be so recognized.
With this three-fold distinction in mind, what should we say about law and other legal
kinds?4 It would seem as though law belongs to the second kind of social kind. It is both
mind-dependent and concept-dependent, but instances of it may not be
conceptdependent, or so I will argue (see Figure 1). Some philosophers of law have claimed that
3The claim that some legal kinds such as habeas corpus or parliament are token-etiological and copied kinds
admittedly depends on how we understand these kinds. On one understanding of what a parliament is, it is a
type of legal institution that can be traced back to the Magna Carta, and nothing can be a parliament unless it
can trace its origin to that particular historical document. But in a looser sense, we could describe the ancient
Athenian assembly as a parliament even though it does not have the same token etiology. On the former
understanding, parliament is a token-etiological and copied kind, whereas on the latter, it is not.
4The claims and arguments in this paragraph derive in part from work-in-progress with Liam Murphy.
law is not concept-dependent, that a society could have law without having a concept of
law (see [
In this paper, I have defended the view that law and other legal kinds are social kinds. Moreover, I have argued that law is an etiological social kind but that it is not a copied kind (in Millikan’s sense). Meanwhile, other legal kinds may be copied kinds, namely those that are descended from a certain origin and have the same provenance, such as some of the legal kinds that pertain to the common law tradition (e.g. jury, habeas corpus). In addition, I have tried to show that law is plausibly regarded not just as a mind-dependent kind, but a concept-dependent social kind, since it is implausible that there can be an institution of law without a concept of law. Laws need to be recognized as such. I have also argued that not every instance of law is a concept-dependent social kind, since there can be individual legal propositions that are not recognized as such. But other legal kinds, such as felon or jury, are likely to be concept-dependent when it comes to their tokens as well as the type.
Is there an ontological difference between legal kinds that are etiological and
those that are not? Are the copied legal kinds different in nature from those that are not
copied? Not necessarily—consider a legal kind like jury. We might take (at least) two
attitudes when it comes to what qualifies as a jury. On one view, an institution is only a
jury if it descends in the right way from certain historical precedents. On another, more
comparative, view of law, an institution is a jury if it plays roughly the same
causalfunctional role in a legal system as juries do in the common law tradition. Thus, the very
same category is sometimes ambiguous between an etiological and a non-etiological
interpretation. Is there an ontological difference between legal kinds that are merely
mind-dependent and those that are additionally concept-dependent? Does the additional
concept-dependence have any ontological implications? Although mind-independence
is often thought to be criterial for realism, I have argued elsewhere [