contingent, individual, and relative, others are permanent,
unchangeable, universal, necessary, and absolute. Now these elements, so
diverse, so opposite, can not have been obtained from the same source;
they must be supplied by separate powers. "Can any man with common sense
reduce under one what _is infallible_, and what is _not
infallible?_"[527] Can that which is "_perpetually becoming_" be
apprehended by the same faculty as that which "_always is?_"[528] Most
assuredly not.

[Footnote 523: Ibid., bk. v. ch. xxii.]

[Footnote 524: Ibid., bk. vii. ch. viii.]

[Footnote 525: Ibid., bk. v. ch. xx.]

[Footnote 526: Ibid., bk. vii. ch. i., ii.]

[Footnote 527: "Republic," bk. v. ch. xxi.]

[Footnote 528: Ibid., bk. v. ch. xxii.; also "Timaeus," Sec. 9.]

These primitive intuitions--the simple perceptions of sense, and the _a
priori_ intuitions of the reason, which constitute the elements of all
our complex notions, have essentially _diverse objects_--the sensible or
ectypal world, seen by the eye and touched by the hand, which Plato
calls doxasten--_the subject of opinion_; and the noetic or archetypal
world, perceived by reason, and which he calls dianontiken--_the subject
of rational intuition or science_. "It is plain," therefore, argues
Plato, "that _opinion_ is a different thing from _science_. They must,
therefore, have a different _faculty_ in reference to a different
object--science as regards that which _is_, so as to know the nature of
real _being_--opinion as regards that which can not be said absolutely
to be, or not to be. That which is known and that which is opined can
not possibly be the same,... since they are naturally faculties of
different things, and both of them are faculties--_opinion_ and
_science_, and each of them different from the other."[529] Here then
are two grand divisions of the mental powers--a faculty of apprehending
universal and necessary Truth, of intuitively beholding absolute
Reality, and a faculty of perceiving sensible objects, and of judging
according to appearance.

[Footnote 529: Ibid., bk. v. ch. xxi., xxii.]

According to the scheme of Plato, these two general divisions of the
mental powers are capable of a further subdivision. He says: Consider
that there are two kinds of things, the _intelligible_ and the
_visible_; two different regions, the intelligible world and the
sensible world. Now take a line divided into two equal segments to
represent these two regions