Whether the Intellect Can Be False?
Objection 1: It would seem that the intellect can be false; for the
Philosopher says (Metaph. vi, Did. v, 4) that "truth and falsehood
are in the mind." But the mind and intellect are the same, as is
shown above (Q. 79, A. 1). Therefore falsehood may be in the mind.
Obj. 2: Further, opinion and reasoning belong to the intellect. But
falsehood exists in both. Therefore falsehood can be in the intellect.
Obj. 3: Further, sin is in the intellectual faculty. But sin involves
falsehood: for "those err that work evil" (Prov. 14:22). Therefore
falsehood can be in the intellect.
_On the contrary,_ Augustine says (QQ. 83, qu. 32), that "everyone
who is deceived, does not rightly understand that wherein he is
deceived." And the Philosopher says (De Anima iii, 10), that "the
intellect is always true."
_I answer that,_ The Philosopher (De Anima iii, 6) compares intellect
with sense on this point. For sense is not deceived in its proper
object, as sight in regard to color; [unless] accidentally through
some hindrance occurring to the sensile organ--for example, the taste
of a fever-stricken person judges a sweet thing to be bitter, through
his tongue being vitiated by ill humors. Sense, however, may be
deceived as regards common sensible objects, as size or figure; when,
for example, it judges the sun to be only a foot in diameter, whereas
in reality it exceeds the earth in size. Much more is sense deceived
concerning accidental sensible objects, as when it judges that
vinegar is honey by reason of the color being the same. The reason of
this is evident; for every faculty, as such, is _per se_ directed to
its proper object; and things of this kind are always the same.
Hence, as long as the faculty exists, its judgment concerning its own
proper object does not fail. Now the proper object of the intellect
is the "quiddity" of a material thing; and hence, properly speaking,
the intellect is not at fault concerning this quiddity; whereas it
may go astray as regards the surroundings of the thing in its essence
or quiddity, in referring one thing to another, as regards
composition or division, or also in the process of reasoning.
Therefore, also in regard to those propositions, which are
understood, the intellect cannot err, as in the case of first
principles from which arises infallible truth in the certitude of
scientific conclusions.
The intellect, however, may be accidentally deceived in the quiddity
of composite things, not by the defect of its organ, for the
intellect is a faculty that is independent of an organ; but on the
part of the composition affecting the definition, when, for instance,
the definition of a thing is false in relation to something else, as
the definition of a circle applied to a triangle; or when a
definition is false in itself as involving the composition of things
incompatible; as, for instance, to describe anything as "a rational
winged animal." Hence as regards simple objects not subject to
composite definitions we cannot be deceived unless, indeed, we
understand nothing whatever about them, as is said _Metaph._ ix, Did.
viii, 10.
Reply Obj. 1: The Philosopher says that falsehood is in the intellect
in regard to composition and division. The same answer applies to the
Second Objection concerning opinion and reasoning, and to the Third
Objection, concerning the error of the sinner, who errs in the
practical judgment of the appetible object. But in the absolute
consideration of the quiddity of a thing, and of those things which
are known thereby, the intellect is never deceived. In this sense are
to be understood the authorities quoted in proof of the opposite
conclusion.
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