Interview August/September 2019 ●Philosophy Now 21hard to imagine that
they would carry on that
way if they agreed that there
was no single correct way to classify
organisms.
There has been some discussion,
including occasionally in scientific jour-
nals, of the application of promiscuous
realism in other fields, including
medicine, economics, and psychiatry. It
has been discussed in relation also to
physical sciences such as chemistry and
astronomy, but here mainly by philoso-
phers. I’m not sure, however, that it is the
kind of thesis that is very relevant to the
day-to-day practice of science, belonging
rather to wider debates about the poten-
tial validity of diverse methodologies.
I might mention that I take one of
the most important audiences for the
position outside the philosophy of sci-
ence to be other parts of philosophy.
Philosophers outside the philosophy of
science still tend to think too much in
terms of a unique set of natural kinds
and the laws that determine their
behaviour. This can have harmful effects
in many areas of philosophy, especially
the philosophy of mind.In 2018 Oxford University Press published a
book edited by you and Daniel Nicholson
called Everything Flows: Towards a Pro-
cessual Philosophy of Biology. What is
process-based biology, and how does it affect
our understanding of living organisms?
A major attraction of process biology for
me is that it can provide a deeper expla-
nation of promiscuous realism. In the
world of things that most philosophers
have assumed – where big things like
organisms are structures of little things
like organs, cells, molecules, and eventu-
ally subatomic particles – pluralism is
just a contingent possibility. Things
might have fallen perfectly into natural
kinds, demarcated by their real, defining
essences, but just happened not to do so.
However, in a world of processes, mat-
ters are different. Our familiar classifica-
tions are static descriptions, a list of
properties that a thing will possess if it is
a member of a particular kind; but in a
world of processes these properties can
only reflect an instantaneous cross-sec-
tion through a world in constant flux.terms. The relations between the pro-
fessional biological terms for biological
kinds and those terms in more common
use, or in use by non-scientific experts
such as gardeners or foresters, seemed
to me much more complex than this.
And indeed a little detailed exploration
confirmed not only the lack of fit
between the scientific and non-scientific
vocabularies, but also that there were
often good reasons for the ways that the
non-scientists divided up the natural
world. Classifications, it seemed to me,
had to be understood and were justified
in terms of the purposes for the classifi-
cations; and the (various) purposes of
scientists were not the same as those of
fishermen, foresters, or furriers.
This was not the first time anyone
had had such an idea, of course. Where
promiscuous realism was somewhat out
of the ordinary was in the realism. Gen-
erally, purpose-relative classification has
gone along with the idea that classifica-
tion is largely a social activity, creating
an order that we impose on the world.
On the contrary, it seemed to me that
the various classifications did respect
real features of the world, and that these
features made our classifications either
well- or ill-suited to our purposes
depending on the purpose. When I later
started describing the world as ‘disor-
dered’, I also argued that there were
many superimposed and interacting
threads of order within, or emerging
from, the disorder. This idea is in
strong contrast, of course, to the still
widely held assumption that the world
only has room for a single unique set of
laws and the division of kinds that they
govern. Much of my subsequent philo-
sophical career might be understood as
following through the implications of
my contrary idea.Do you think that if biologists and others
adopt promiscuous realism, this would affect
something in a ‘real science-making’ way?
It certainly might have an effect on the
science it most directly addresses, sys-
tematics. As readers of David Hull’s
wonderful book, Science as a Process
(1990), will know, debates among propo-
nents of different schools of taxonomy
can be acrimonious and even vicious. It’sDo you think the most famous figure in
biology, Charles Darwin, was more of a
natural scientist, a natural philosopher, or a
mixture of both?
‘Natural philosopher’ is a nice term that
we’ve pretty much lost, and I think it
would fit Darwin very well. I would say,
though, that despite having revolution-
ary ideas that have undoubtedly had
profound effects on philosophy, there
are respects in which he very much
belongs in the category of scientist. We
can perhaps focus too much on The Ori-
gin of Species and The Descent of Man , and
not enough on his work, for example, on
pollination or earthworms. This work
shows the care, patience, and experi-
mental ingenuity that are very much
characteristics of scientists rather than
philosophers. But certainly he thought
deeply and synthetically about the
implications of all this detailed scientific
work, so I’d be happy to use any or all of
the labels you suggested.
You’ve made a substantial contribution to
many topics in the philosophy of biology, but
there are a few that I’d especially like to ask
about. Firstly, one concept endorsed by you is
promiscuous realism. Could you briefly
tell us what it is?
‘Promiscuous realism’ was an idea that
came out of my very early work on tax-
onomy. It actually began in response to
an idea of the analytical philosopher
Hilary Putnam that was very influential
in the 1970s and 80s. Putnam was inter-
ested in the reference of general terms,
and particularly of so-called ‘natural
kind’ terms – the words we use for
things that exist naturally as individuals.
He suggested that natural kind terms in
our everyday language, for example our
names for kinds of animals and plants,
were intended to refer to the real natu-
ral kinds – the real natures or essences
of things which would eventually be dis-
covered by science. So, famously, scien-
tists eventually discovered that water is
H 2 O, and this filled a kind of blank in
the meaning of the term ‘water’.
Anyway, Putnam suggested that in
biology a similar blank in terms such as
‘tiger’ or ‘lemon’ would eventually be
filled by a knowledge of genetics. This
seemed wrong to me, at least for species
Interview