tion of real being."[444] Therefore Plato
inscribed over the door of his academy, "Let none but Geometricians
enter here." To the mind thus disciplined in abstract thinking, the
conceptions and ideas of reason have equal authority, sometimes even
superior authority, to the perceptions of sense.

[Footnote 444: Alcinous, "Introduction to the Doctrines of Plato," ch.
vii.]

Now if the testimony of both reason and sense, as given in
consciousness, is accepted as of equal authority, and each faculty is
regarded as, within its own sphere, a source of real, valid knowledge,
then a consistent and harmonious system of _Natural Realism_ or _Natural
Dualism_ will be the result. If the testimony of sense is questioned and
distrusted, and the mind is denied any immediate knowledge of the
sensible world, and yet the existence of an external world is maintained
by various hypotheses and reasonings, the consequence will be a species
of _Hypothetical Dualism_ or _Cosmothetic Idealism_. But if the
affirmations of reason, as to the unity of the cosmos, are alone
accepted, and the evidence of the senses, as to the variety and
multiplicity of the world, is entirely disregarded, then we have a
system of _Absolute Idealism_. Pythagoras regarded the harmony which
pervades the diversified phenomena of the outer world as a manifestation
of the unity of its eternal principle, or as the perpetual evolution of
that unity, and the consequent _tendency_ of his system was to
depreciate the _sensible_. Following out this tendency, the Eleatics
first neglected, and finally denied the variety of the universe--denied
the real existence of the external world, and asserted an absolute
_metaphysical_ unity.

_Xenophanes of Colophon_, in Ionia (B.C. 616-516), was the founder of
this celebrated school of Elea. He left Ionia, and arrived in Italy
about the same time as Pythagoras, bringing with him to Italy his Ionian
tendencies; he there amalgamated them with Pythagorean speculations.

Pythagoras had succeeded in fixing the attention of his countrymen on
the harmony which pervades the material world, and had taught them to
regard that harmony as the manifestation of the intelligence, and unity,
and perfection of its eternal principle. Struck with this idea of
harmony and of unity, Xenophanes, who was a poet, a rhapsodist, and
therefore by native tendency, rather than by intellectual discipline, an
Idealist, begins already to attach more importance to _uni