The Development of the Philosophy of Species 287
exists, or whether the two still-distinct lineages M and N are A or not. After all, this
is the case when we discuss nascent species anyway. But this seems counterintuitive
as well—if ontology is what we are discussing, then each lineage, say M, is identical
physically to A, and all that is missing is a date indexical. This seems odd.
For this reason, Ruse wants to treat A as a class which can be instantiated in
actual historical entities or processes as many times as need be. It avoids the respe-
ciation problem. The disagreement lies in different answers to the question, “what
do we need to capture in our metaphysics for things that can arise more than once?”
Consider a different problem—that of the identity of Individual^20 persons. We typi-
cally say of an Individual that he or she has some terminus a quo at a particular
point—it might be conception, or nativity, or some point of development. In taxo-
nomic terms, we would say that this Individual is monophyletic, being the ancestral
cell population and all descendent cell populations. But it is possible, in biology,
for an Individual fetus to be a mixture of two genetically distinct fertilized cells or
zygotes; these are called chimera after the mythical monster. Are these Individuals,
in the ordinary sense? And to make matters worse, what if one zygote had been com-
menced in vitro some years before the second and frozen in nitrogen before it was
fused with the other? What is the terminus a quo?
If we want to capture this case in our definitions of what it is to be an Individual,
then we have the same sorts of problems for identity of organisms that we have for
species, and how we deal with them will depend largely on how we think meaning
inheres in such terms. We might say that to be an Individual, say Socrates, to use the
classic example, is to instantiate Socratic properties—that is, to treat Socrates as a
class that can be instantiated in many different individuals courtesy of some science
fiction replicating machine. That would be what Ruse would say about species. Or,
we could say that there is only one Socrates, who was born, perhaps chimerically,
at a relatively exact period, only in this case the chimeric Socrates was “born” or
“begun” in an extended process unlike the monophyletic Individuals we usually see.
Even if the unfused zygotes were viable and developing organisms, we might say
that they ceased to be upon being fused; and so on for all the exotic cases we might
imagine.
Chimeric species are not a counterexample to our intuitions of what species are,
metaphysically speaking; they may extend our conception, or we might (arbitrarily)
exclude them, but I see no reason to reject the individuality thesis because of these
cases and be forced to instead adopt a “natural kind” class conception of the species
categorical term. What we choose as the boundary for the term may be arbitrary or
it may be forced by the biological realities, but species are still, as Caplan phrased
it,^21 déclassé, I think.
(^20) I am capitalizing the word “Individual” to avoid confusion with the metaphysical notion being dis-
cussed here.
(^21) Caplan 1980.