312 Species(a philosopher, although he studied biology and history of biology) have brought
those resources to bear on species from a metaphysical and analytic perspective.
Elliot Sober has likewise invoked epistemology to deal with issues of phylogenetic
systematics and evolution.^85
This philosophical influence on biology is nothing new. Apart from the ubiquitous
Popper, mathematical philosophers have strongly influenced the development of sys-
tematics. Russell and Whitehead’s Principia Mathematica inspired J. H. Woodger to
recast biology in terms of symbolic logic.^86 This in turn greatly influenced Hennig’s
phylogenetic systematics, and the resulting terms of grouping and order of branching
that are now common property to biologists of all philosophies.^87
When Mill discussed logical classification, he revived the scholastic conception
of the relation between differentiae and relata. Unlike the medieval philosophers,
however, Mill was concerned with causal, not formal or logical, differentiae and
relata. It is this tension, between wanting to carve nature at its joints and yet return-
ing to carving language at its joints, that continually recurs throughout western phi-
losophy. To pre-empt this recurrence, consider how species differentiate themselves,
rather than how we might do that, in the hope that systematics can retrieve the natu-
ral self-classification of the organisms themselves, but not in the expectation that it
always will.
Family Resemblance
Wittgenstein and Resemblance
Are species family resemblance terms?^88 In the famous and often-discussed sections
66 and 67 of the Philosophical Investigations, Wittgenstein discusses what is com-
mon to all games, and argues that if one does not assume that the term game has
something common by definition but instead “looks and sees,”
... you will not see something that is common to all, but similarities, relationships,
and a whole series of them at that. ... we see a complicated network of similarities
overlapping and criss-crossing: sometimes overall similarities, sometimes similarities
of detail. ... I can think of no better expression to characterize these similarities than
“family resemblances”; for the various resemblances between members of a family:
build, features, colour of eyes, gait, temperament, etc. etc. overlap, and criss-cross in
the same way.—And I shall say, ‘games’ form a family.”This is an account of names, and it is curious that Wittgenstein applied an anal-
ogy between naming and resemblance based on inheritance. For species terms are
names, and their extension is just such a crisscrossing of inheritance lines and related
individuals. As I understand the family resemblance predicate (FRP) notion, it sug-
gests that the extension of such a predicate is a cluster of intersecting sets, but not(^85) Sober 1988, Sober and Steel 2002, Sober 2008.
(^86) It should be noted that Woodger was a zoologist by training.
(^87) See Varma 2013 for a review.
(^88) Several authors have proposed that they are: e.g., Pigliucci 2003, Ereshefsky 2010, Kull 2016.