An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

188 DEFINITION.
goes back to Plato. It has been adopted by the
mediaeval and formal logicians because it appears to
provide a theory of division which does not make the
process depend entirely on the matter of our knowledge,
as classification does ( 8). But division by dichotomy
is no more independent of our knowledge of the facts
than any other kind of classification. This is clearly
shown by Aristotle in criticising Plato s view of the
process (An. Prior., i. 31). Plato appeared to claim
that by this process we might discover definitions, or at
least prove them. Thus it was thought that we could
discover what
"
"
man is by taking a suitable summum
genus to which (we decide) man belongs i.e., Substance
or Being. This we divide into
"
corporeal
"
and "not
being ; then, deciding that man belongs to
"
corporeal
the former class, corporeal substance or body, we divide
this into
"
organic bodies
"
and bodies
"
not organic,"
and decide that man belongs to the former ; and so on.
Each pair of terms are contradictories, and the result
may be expressed in a table which was afterwards called
the
"
"
Tree of :
Porphyry
organic
i.e., living being
I
Substance
" J_
f
I
corporeal not corporeal
i.e., body
1
"I
sentient not sentient
i.e., animal
rational not rational
i.e., man
I
Socrates Plato and others
I
|
not organic