Michael Moore aims primarily, but not exclusively, at providing legal scholars and others with a defensible naturalist ontology of law and legal phenomena. Accordingly, he defends: (1) an account of scientific, mental, moral, and legal properties, according to which there are not only natural kinds, but also moral and functional kinds, and (2) a causal theory of word meaning, according to which natural, moral and functional kind words get their meaning not from a list of conventionally accepted criteria, or from conventionally accepted exemplars, but from the natural, moral, or functional kinds to which they refer. He maintains, more specifically, (1A) that distinctively legal phenomena, such as legal rights, legal duties, precedent, malice, etc. are functional kinds, in the sense that they have a nature that consists not in their structure, but in the function they fulfill in law (or in a given legal order), and (1B) that the function of a functional kind is that effect, or those effects, of the functional kind that causally contribute more than does any of its other effects to the goal of the larger system within which it occurs. He also maintains, (1C) that functional kinds can be reduced to indefinitely large disjunctions of natural properties, (1D) that the relevant version of reductionism is metaphysically reductionist naturalism, and (1E) that functional kinds play an indispensable role in the explanation of human behavior. I am inclined to agree with Moore that there is no escaping metaphysics in legal thinking, and that any legal metaphysics should be naturalistic. I am, however, going to argue: (i) that the method for determining the function of a (purported) functional kind proposed by Moore is too indeterminate to be able to pin down the function in an unequivocal way; that this suggests, though it does not entail, that there is no fact of the matter as regards the question of what the function is of a (purported) functional kind, and that there seems to be no way to remedy this troublesome indeterminacy. I am also going to argue – assuming, for the sake of argument, that functional kinds do exist and that we can determine their function using Moore’s method – (ii) that it turns out to be very difficult to identify the properties that are part of the indefinitely large disjunction of natural properties which, on Moore’s analysis, is identical to a functional kind, and that this suggests, as things stand, that Moore’s claim that functional kinds can be reduced to such disjunctions is too abstract to be illuminating; and (iii) that the so-called logical connection argument, which requires that cause and effect be logically distinct in a functional causal explanation of an action or event, does not undermine Moore’s account of functional kinds. Furthermore, I am going to argue, (iv) that functional kinds cannot be part of the best explanation of human behavior, because they lack systematic (or nomological) unity, and that they lack such unity because they are necessarily multiply realizable, in the sense that they can be realized on different occasions by different first-order properties that may have very different causal powers; and (v) that Moore will therefore have to give up: (a) the view that functional kinds are identical to indefinitely large disjunctions of natural properties, or (b) the view that functional kinds are part of the best explanation of human behavior, or both; that if he drops (a), his naturalism will be undermined, or at least seriously threatened, and that if he drops (b), he will have to admit either that functional kinds do not exist or that they are not as interesting as they seem. On the basis of claims (i), (ii), (iv), and (v), I am also going to argue: (vi) that the idea of a functional kind should not play a central role in any theory of law or legal reasoning, or in any other theory of a legal phenomenon. Finally, I am going to suggest (vii) that the way forward in the field of the metaphysics of law is to explore a version of anti-realism, namely, conventionalism.
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Jul 30, 2018
Simon J Evnine 
Open Access
