298 Species(independently or convergently evolved) or a paraphyletic (privatively defined as a
clade minus some branches) group.
So what are the differences between NKs and NGs? I claim that these are the
following.- NKs are timeless abstractions that are only instantiated or realized, while
NGs are concrete objects that change when their constituents do. - NKs are realized by indiscernibles, while NGs are collections of discern-
ible particulars. - NGs are historical objects, with a commencement and cessation point and a
location. - NGs comprise objects that form causal chains, or lineages in biology, over
time.
These are the features of biological classes. How do they apply outside biology?
What distinguishes all NKs from all NGs? It is my opinion that the difference lies
in one being defined by a model, and the other comprising causal relations between
objects. And at the foundation, the root, of an “ultimate physics,” they may very well
coincide.
NGs are formed in biology by the transmission of genes, epigenetic systems,
environments, learning, and behaviors. These things cause members of a species to
resemble each other and to have much the same physical properties, or phenotypes.
Out of a universe of physical properties they might have had, only those that are
passed on to them and which they are competent to achieve directly as a result of what
is passed onto them are those they do have. There is no definite microstructure for an
NG, although genotypes are often mostly the same for most members of a species.
NKs, on the other hand, are always exemplified in the same manner by anything
that is an exemplar of that NK. It is definitionally required, for example, that all
predators are heterotrophs. There are many physical ways by which this can happen,
but all NK-objects have only one way to be that NK (by consuming other organisms,
for example). In short, NKs are fully populated possibility spaces, while NGs are
only sparsely populated. Every possible state in the possibility space allowed for by
the intension of the NK is a full and total member of the NK, an indiscernible. But
of an NG, only those that actually do result from the shared causal processes are
members of the class. Hence, members of an NK must have a shared microstructure.
This is not a causal requirement, but one of definition—it is to be (esse) that kind to
have that microstructure (essence).
When Locke made the point about the difference between relation of the linguistic
and familial kinds, he was in effect noting that causal or generative relations between
entities—the natural relations, as he calls them—form groups that are subsequently
named.^44 The implication is that, as Locke notes elsewhere, these names need not
(^44) This appears to contradict Locke’s claim elsewhere in the Essay (II.xx.4, II.xxv.8) that relations exist
only in the mind. His usual exactness of expression slips here. It is possible that he did think the rela-
tions between dam and foal were merely conceptual, but genealogies are formed on observation, not
comparison of ideas naming the relata, as he claims relations are (II.xxv.2). See Stewart 1980 for a
discussion (reprinted in Thiel 2002).