Species

24 Species

a species was a member of a broader group—a genus—that was formed by a predicate.
There was no necessity for any object to be a member of a single genus, and a spe-
cies might be, with respect to some other predicate a genus in its own right. In short,
species were predicate-relative individuals. They were whatever was differentiable
out of the genus. This gave rise to Porphyry’s dichotomous notion of classication.
Porphyry of Tyre (c. 234–c. 305 ), a student of Plotinus (c. 204/5–270 ),
syncretized Plato’s dichotomous method with Aristotle’s logical division of predi-
cables. Aristotle’s conception of the infimae species was primarily a matter of logical
analysis. Porphyry combined this and Plato’s method of classication in the Sophist
to produce what became known as Por phyr y’s com b or tree (Arbor Porphyriana) in
the later Middle Ages (Figure 1.2). Porphyry treated species slightly differently than
Aristotle. In place of the four predicables of Aristotle, Porphyry had ve: genus, dif-
ference, species, property, and accident, replacing definition with species.^118
Boëthius reported that Porphyry had raised the issue of whether species and gen-
era exist only in the mind:

As for genera and species, [Porphyry] says, I shall decline for the present to say

(1) whether they subsist or are posited in bare [acts of] understanding only, (2) whether,

if they subsist, they are corporeal or incorporeal, and (3) whether [they are] separated

from sensibles or posited in sensibles and agree with them. For that is a most noble

matter, and requires a longer investigation.^119

This began what we now know as the “Universals” debate^120 and led, fairly
directly, to the position that came to be known as nominalism.

(^118) Cf. Barnes’ commentary §0 in Porphyry 2003, 26–32, also see Joseph 1916, chapter IV. As noted,
Joseph’s book has been implicated in the adoption by Cain and Hull of the notion that pre-evolutionary
species are timeless and static entities dened by their essences. It should be noted that Joseph is
presenting a formal account of the pre-set theoretic logics from Aristotle until his day, and he does,
in several places (pp 53n, 92–96), note the differences between Aristotle and Porphyry, but it would
not have been obvious to anyone not familiar with the technical aspects of the medieval commentar-
ies on Porphyry. Joseph’s book is actually a very good late example of the treatment of logic in the
Aristotelian tradition, surviving into the post-Darwinian era but aware of it (pp 473–475). Hull 1967,
310−313 cites a passage from the rst edition of 1905 in which Joseph notes that the evolution of spe-
cies is not thought of by biologists in the logical sense, but I cannot nd it in either edition. However,
Joseph does say this in the rst edition:
(^) But now that the theory of organic evolution has reduced the distinction between varietal
and specic difference to one of degree, the task of settling what is the essence of a species
becomes theoretically impossible. It is possible to describe a type; but there will be hundreds
of characteristics typical of every species [page 82].
(^119) The passage is translated from Anicii Manlii Severini Boethii In Isagogen Porphyrii commenta, edi-
tio 2a, lib. I, ca. 10–11, Samuel Brandt, ed., p. 159 line 3–p. 167 line 20. Translation by Paul Spade,
unpublished, used with permission. Barnes’ direct translation of Porphyry [Porphyry 2003, 3, lines
10 –15] reads:
(^) For example, about genera and species—whether they subsist, whether they actually depend
on bare thoughts alone, whether if they actually subsist they are bodies or incorporeal and
whether they are separable or are in perceptible items and subsist about them—these matters
I shall decline to discuss, such a subject being very deep and demanding another and a larger
investigation.
(^120) Klima 2013. For a full discussion, see Aaron 1952.