The Classical Era: Science by Division 25Why did Porphyry even raise this question? It seems to come out of nowhere.
Aristotle had no doubt that the eidos was real—it was the form of the thing that
existed as a material object. Plato had no such doubt either—to him only Ideas were
real.^122 I suspect that Porphyry was responding to the debates over atomism that
bridge the period of Aristotle and the Epicureans, to his day, around 500 years’ dura-
tion. Plotinus had addressed the arguments of the Gnostics in his Enneads, which
Porphyry had edited. It is also possible that the topic had indeed been raised by
(^121) Oldroyd 1983, 29.
(^122) And interestingly, until late in the seventeenth century, “Realism” denoted a realism about ideas;
what we would consider Idealism today [Blackmore 1979, Aaron 1952].
Substance
Incorporeal Corporeal
Inanimate Animate
Insensitive Sensitive
Irrational Rational
Socrates Aristotle Individuals
Differentia
Differentia
Differentia
Differentia
Individua
Summum Genus
Subaltern genus: Body
Subaltern genus: Living
Subaltern genus: A nimal
Infima species: Human
A
Body
Substance
Incorporeal
Inanimate
Insensitive
Irrational
Aristotle
Living
Animal
Human
Socrates Plato
Rational
Sensitive
Animate
Corporeal
Summum Genus
Differentia
Differentia
Differentia
Differentia
Subaltern Genus
Subaltern Genus
Subaltern Genus
Infima Species
Individuals
B
FIGURE 1.2 The Tree of Porphyry, compared with a cladogram. Version A has been adapted
from Oldroyd^121 to make the logical isomorphism with a cladogram clearer—the traditional
form of Porphyry’s tree is more like the one Oldroyd presents (B). (Continued)