Aristotle
this antithesis between the world of Universals or Cogitables, which
are the only unchangeable realities and the only objects of
knowledge,--and the world of Sensible Particulars, which are
transitory and confused shadows of these Universals, and are objects
of opinion only. Full and real Ens is knowable, Non-Ens is altogether
unknowable; what is midway between the two is matter of opinion, and
in such midway are the Particulars of sense.[7] Respecting these
last, no truth is attainable: whenever you affirm a proposition
respecting any of them, you may with equal truth affirm the contrary
at the same time. Nowhere is the contrast between the Universals or
real Ideas (among which the Idea of Good is the highest, predominant
over all the rest), and the unreal Particulars, or Percepta, of
Sense, more forcibly insisted upon than in the Republic. Even the
celestial bodies and their movements, being among these Percepta of
sense, are ranked among phantoms interesting but useless to observe;
they are the best of all Percepta, but they fall very short of the
perfection that the mental eye contemplates in the Ideal--in the true
Figures and Numbers, in the real Velocity and the real Slowness. In
the simile commencing the seventh book of the Republic, Plato
compares mankind to prisoners in a cave, chained in one particular
attitude, so as to behold only an ever-varying multiplicity of
shadows, projected, through the opening of the cave upon the wall
before them, by certain unseen realities behind. The philosopher is
one among a few, who by training or inspiration, have been enabled to
face about from this original attitude, and to contemplate with his
mind the real unchangeable Universals, instead of having his eye
fixed upon their particular manifestations, at once shadowy and
transient. By such mental revolution he comes round from the
Perceivable to the Cogitable, from Opinion to Knowledge.
[Footnote 7: Plato, Republic. v. pp. 477, 478.]
The distinction between these two is farther argued in the elaborate
dialogue called Theætetus, where Sokrates, trying to explain what
Knowledge or Cognition is, refutes three proposed explanations and
shows, to his own satisfaction, that it is not sensible perception,
that it is not true opinion, that it is not true opinion coupled with
rational explanation. But he confesses himself unable to show what
Knowledge or Cognition is, though he continues to announce it as
correlating with Realities Cogitable and Universal only.[8]
[Footnote 8: Plato, Theætêt. pp. 173, 176, 186. Grote's Plato, II.
xxvi. pp. **320-395.]
In the passages above noticed, and in many others besides, we find
Plato drawing a capital distinction between Universals eternal and
unchangeable (each of them a Unit as well as a Universal),[9] which
he affirms to be the only real Entia,--and Particulars transient and
variable, which are not Entia at all, but are always coming or going;
the Universals being objects of cogitation and of a psychological
fact called Cognition, which he declares to be infallible; and the
Particulars being objects of Sense, and of another psychological fact
radically different, called Opinion, which he pronounces to be
fallible and misleading. Plato holds, moreover, that the Particulars,
though generically distinct and separate from the Universals, have
nevertheless a certain communion or participation with them, by
virtue of which they become half existent and half cognizable, but
never attain to full reality or cognizability.
[Footnote 9: Plato, Philêbus, p. 15, A. B.; Republic, x. p. 596, A.
The phrase of Milton, "unus et universus," expresses this idea; also
the lines:--
"Sed quamlibet natura sit communior,
Tamen seorsus extat ad modum unius," &c.]
This is the first statement of the theory of complete and unqualified
Realism, which came to be known in the Middle Ages under the phrase
_Universalia ante rem_ or _extra rem_, and to be distinguished from
the two counter-theories _Universalia in re_ (Aristotelian), and
_Universalia post rem_ (Nominalism). Indeed, the Platonic theory goes
even farther than the phrase _Universalia ante rem_, which recognizes
the particular as a reality, though posterior and derivative; for
Plato attenuates it into phantom and shadow. The problem was now
clearly set out in philosophy--What are the objects correlating with
Universal terms, and with Particular terms? What is the relation
between the two? Plato first gave to the world the solution called
Realism, which lasted so long after his time. We shall presently find
Aristotle taking issue with him on both the affirmations included in
his theory.
But though Plato first introduced this theory into philosophy, he was
neither blind to the objections against it, nor disposed to conceal
them. His mind was at once poetically constructive and dialectically
destructive; to both these impulses the theory furnished ample scope,
while the form of his compositions (separate dialogues, with no
mention of his own name) rendered it easy to give expression either
to one or to the other. Before Aristotle arose to take issue with
him, we shall find him taking issue with himself, especially in the
dialogues called Sophistes and Parmenides, not to mention the
Philêbus, wherein he breaks down the unity even of his sovereign
Idea, which in the Republic governs the Cogitable World,--the Idea of
Good.[10]
[Footnote 10: Plato, Philêbus, pp. 65, 66. See Grote's Plato, II.
xxx. pp. 584, 585.]
Both in the Sophistes and in the Parmenides, the leading disputant
introduced by Plato is not Sokrates, but Parmenides and another
person (unnamed) of the Eleatic school. In both dialogues objections
are taken against the Realistic theory elsewhere propounded by Plato,
though the objections adduced in the one are quite distinct from
those noticed in the other. In the Sophistes, the Eleatic reasoner
impugns successfully the theories of two classes of philosophers, one
the opposite of the other: first, the Materialists, who recognized no
Entia except the Percepta of Sense; next, the Realistic Idealists,
who refused to recognize these last as real Entia, or as anything
more than transient and mutable Generata or Fientia, while they
confined the title of Entia to the Forms, cogitable, incorporeal,
eternal, immutable, neither acting on anything, nor acted upon by
anything. These persons are called in the Sophistes "Friends of
Forms," and their theory is exactly what we have already cited out of
so many other dialogues of Plato, drawing the marked line of
separation between Entia and Fientia; between the Immutable, which
alone is real and cognizable, and the Mutable, neither real nor
cognizable. The Eleate in the Sophistes controverts this Platonic
theory, and maintains that among the Universal Entia there are
included items mutable as well as immutable; that both are real and
both cognizable; that Non-Ens (instead of being set in glaring
contrast with Ens, as the totally incogitable against the infallibly
cognizable)[11] is one among the multiplicity of Real Forms, meaning
only what is different from Ens, and therefore cognizable not less
than Ens; that Percepta and Cogitata are alike real, yet both only
relatively real, correlating with minds percipient and cogitant.
Thus, the reasoning in the Sophistes, while it sets aside the
doctrine of _Universalia ante rem_, does not mark out any other
relation between Universals and Particulars (neither _in re_ nor
_post rem_). It discusses chiefly the intercommunion or reciprocal
exclusion of Universals with respect to each other; and upon this
point, far from representing them as objects of infallible Cognition
as contrasted with Opinion, it enrolls both Opinion and Discourse
among the Universals themselves, and declares both of them to be
readily combinable with Non-Ens and Falsehood. So that we have here
error and fallibility recognized in the region of Universals, as well
as in that of Particulars.
[Footnote 11: Plato, Republic, v. pp. 478, 479.]
But it is principally in the dialogue Parmenides that Plato discusses
with dialectical acuteness the relation of Universals to their
Particulars; putting aside the intercommunion (affirmed in the
Sophistes) or reciprocal exclusion between one Universal and another,
as an hypothesis at least supremely difficult to vindicate, if at all
admissible.[12] In the dialogue, Sokrates is introduced in the
unusual character of a youthful and ardent aspirant in philosophy,
defending the Platonic theory of Ideas as we have seen it proclaimed
in the Republic and in the Timæus. The veteran Parmenides appears as
the opponent to cross-examine him; and not only impugns the theory by
several interrogatories which Sokrates cannot answer, but also
intimates that there remain behind other objections equally serious
requiring answer. Yet at the same time he declares that, unless the
theory be admitted, and unless _Universalia ante rem_ can be
sustained as existent, there is no trustworthy cognition attainable,
nor any end to be served by philosophical debate. Moreover,
Parmenides warns Sokrates that, before he can acquire a mental
condition competent to defend the theory, he must go through numerous
preliminary dialectical exercises; following out both the affirmative
and the negative hypotheses in respect to a great variety of
Universals severally. To illustrate the course prescribed, Parmenides
gives a long specimen of this dialectic in handling his own doctrine
of Ens Unum. He takes first the hypothesis _Si Unum est_, next the
hypothesis _Si Unum non est_; and he deduces from each, by ingenious
subtleties, double and contradictory conclusions. These he sums up at
the end, challenging Sokrates to solve the puzzles before affirming
his thesis.
[Footnote 12: Plato, Parmenid. p. 129, E.; with Stallbaum's
Prolegomena to that dialogue, pp. 38-42.]
Apart from these antinomies at the close of the dialogue, the
cross-examination of Sokrates by Parmenides, in the middle of it,
brings out forcibly against the Realistic theory objections such as
those urged against it by the Nominalists of the Middle Ages. In the
first place, we find that Plato conceived the theory itself
differently from Porphyry and the philosophers that wrote subsequently
to the Peripatetic criticism. Porphyry and his successors put the
question, Whether Genera and Species had a separate existence, apart
from the Individuals composing them? Now, the world of Forms (the
Cogitable or Ideal world as opposed to the Sensible) is not here
conceived by Plato as peopled in the first instance by Genera and
Species. Its first tenants are _Attributes_, and attributes distinctly
_relative_--Likeness, One and Many, Justice, Beauty, Goodness, &c.
Sokrates, being asked by Parmenides whether he admits Forms
corresponding with these names, answers unhesitatingly in the
affirmative. He is next asked whether he admits forms corresponding
to the names Man, Fire, Water, &c., and, instead of replying in the
affirmative, intimates that he does not feel sure. Lastly, the
question is put whether there are Forms corresponding to the names
of mean objects--Mud, Hair, Dirt, &c. At first he answers
emphatically in the negative, and treats the affirmative as
preposterous; there exist no cogitable Hair, &c., but only the object
of sense that we so denominate. Yet, on second thoughts, he is not
without misgiving that there may be Forms even of these; though the
supposition is so repulsive to him that he shakes it off as much as
he can. Upon this last expression of sentiment Parmenides comments,
ascribing it to the juvenility of Sokrates, and intimating that, when
Sokrates has become more deeply imbued with philosophy, he will cease
to set aside any of these objects as unworthy.