Whether Truth Is Immutable?
Objection 1: It seems that truth is immutable. For Augustine says (De
Lib. Arbit. ii, 12), that "Truth and mind do not rank as equals,
otherwise truth would be mutable, as the mind is."
Obj. 2: Further, what remains after every change is immutable; as
primary matter is unbegotten and incorruptible, since it remains after
all generation and corruption. But truth remains after all change; for
after every change it is true to say that a thing is, or is not.
Therefore truth is immutable.
Obj. 3: Further, if the truth of an enunciation changes, it changes
mostly with the changing of the thing. But it does not thus change.
For truth, according to Anselm (De Verit. viii), "is a certain
rightness" in so far as a thing answers to that which is in the
divine mind concerning it. But this proposition that "Socrates sits",
receives from the divine mind the signification that Socrates does
sit; and it has the same signification even though he does not sit.
Therefore the truth of the proposition in no way changes.
Obj. 4: Further, where there is the same cause, there is the same
effect. But the same thing is the cause of the truth of the three
propositions, "Socrates sits, will sit, sat." Therefore the truth of
each is the same. But one or other of these must be the true one.
Therefore the truth of these propositions remains immutable; and for
the same reason that of any other.
_On the contrary,_ It is written (Ps. 11:2), "Truths are decayed from
among the children of men."
_I answer that,_ Truth, properly speaking, resides only in the
intellect, as said before (A. 1); but things are called true in
virtue of the truth residing in an intellect. Hence the mutability of
truth must be regarded from the point of view of the intellect, the
truth of which consists in its conformity to the thing understood. Now
this conformity may vary in two ways, even as any other likeness,
through change in one of the two extremes. Hence in one way truth
varies on the part of the intellect, from the fact that a change of
opinion occurs about a thing which in itself has not changed, and in
another way, when the thing is changed, but not the opinion; and in
either way there can be a change from true to false. If, then, there
is an intellect wherein there can be no alternation of opinions, and
the knowledge of which nothing can escape, in this is immutable truth.
Now such is the divine intellect, as is clear from what has been said
before (Q. 14, A. 15). Hence the truth of the divine intellect is
immutable. But the truth of our intellect is mutable; not because it
is itself the subject of change, but in so far as our intellect
changes from truth to falsity, for thus forms may be called mutable.
Whereas the truth of the divine intellect is that according to which
natural things are said to be true, and this is altogether immutable.
Reply Obj. 1: Augustine is speaking of divine truth.
Reply Obj. 2: The true and being are convertible terms. Hence just as
being is not generated nor corrupted of itself, but accidentally, in
so far as this being or that is corrupted or generated, as is said in
_Phys._ i, so does truth change, not so as that no truth remains, but
because that truth does not remain which was before.
Reply Obj. 3: A proposition not only has truth, as other things are
said to have it, in so far, that is, as they correspond to that which
is the design of the divine intellect concerning them; but it is said
to have truth in a special way, in so far as it indicates the truth
of the intellect, which consists in the conformity of the intellect
with a thing. When this disappears, the truth of an opinion changes,
and consequently the truth of the proposition. So therefore this
proposition, "Socrates sits," is true, as long as he is sitting, both
with the truth of the thing, in so far as the expression is
significative, and with the truth of signification, in so far as it
signifies a true opinion. When Socrates rises, the first truth
remains, but the second is changed.
Reply Obj. 4: The sitting of Socrates, which is the cause of the
truth of the proposition, "Socrates sits," has not the same meaning
when Socrates sits, after he sits, and before he sits. Hence the
truth which results, varies, and is variously signified by these
propositions concerning present, past, or future. Thus it does not
follow, though one of the three propositions is true, that the same
truth remains invariable.
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