The Development of the Philosophy of Species 295
class. It would therefore necessarily follow that a member of one species would liter-
ally give birth to a member of another just at the point at which the intrinsic property
set is modified or lost, and another gained. Any organism that retained the essen-
tial characters of the ancestral species and gained the essential characters of a new
one would simultaneously be a member of both species. Add to this the fact that
most species are polytypic for the majority of their genes and morphological char-
acters, and it becomes likely there is no intrinsic property set for all and only mem-
bers of all species. Some views of species, such as some phylogenetic conceptions
(“Phylogenetic Taxon” conceptions) have indeed defined species as differentiable
or diagnosable groups of organisms which do not vary (thus increasing the number
of species beyond reproductively isolated groups), but typically, species are thought
to be delineated de re rather than de dicto, and to vary in any candidate physical
“essence” or JNSSPs. (What is true of species is true, mutatis mutandis, of higher
and lower taxa.) As NKs are tied to universals, and in particular laws of nature, the
question must arise, and has repeatedly done, whether there are laws in biology, and
natural kinds of living things. It may pay therefore to compare the attributes of the
object classes of physical NKs with the attributes of candidate object classes of biol-
ogy, such as organisms, taxa, or ecotypes. How do they critically differ, if they do?
Indiscernibles...............................................................................
Universal objects in physics are typically indiscernibles. One electron differs only
from another in exogenous properties such as location and velocity. Its endogenous
properties, such as charge and mass, are identical to every other electron (this argu-
ment is put clearly by Hull and Ghiselin). The same is true, pace isotopes, of atoms
of gold, pace isomers, of molecules of amino acids and electromagnetic radiations of
identical wavelengths. With biological classes, though, it is different. In physics, laws
apply universally because the same entities are covered by that law in each applica-
tion of it. But in biology, each organism, each molecular gene, each cell is distinct,
even when these entities fall under “the same” class, taxonomically speaking. Like
snowflakes,^36 each biological object is intrinsically an individual. Unlike snowflakes,
the similarity relations between organic entities are statistical rather than the result
of deterministic causal processes under boundary conditions. It is arguable whether
this is true even for snowflakes. Physical objects might never, in fact, be rigidly
determined by causal laws. But whether there is a qualitative difference or not, bio-
logical organisms, at least, do fall into distributions over a sample set or population.
Organic systems are also subject to a complex range of boundary conditions, as well
as having unique beginner states, but if this is the only difference, the indiscernibles
involved are still only those of physics (and chemistry), and as such biological organ-
isms remain subject to physicochemical laws such as the laws of thermodynamics.
There appear to be no universal laws of biology that are not laws of physics over
(^36) So far as we know...