deficiency in two ways.
First, on the part of the object, secondly, on the part of the act. On
the part of the object, because the true essentially denotes a kind of
equality, and equal is a mean between more and less. Hence for the
very reason that a man says what is true about himself, he observes
the mean between one that says more than the truth about himself, and
one that says less than the truth. On the part of the act, to observe
the mean is to tell the truth, when one ought, and as one ought.
Excess consists in making known one's own affairs out of season, and
deficiency in hiding them when one ought to make them known.
_______________________

SECOND ARTICLE [II-II, Q. 109, Art. 2]

Whether Truth Is a Special Virtue?

Objection 1: It seems that truth is not a special virtue. For the
true and the good are convertible. Now goodness is not a special
virtue, in fact every virtue is goodness, because "it makes its
possessor good." Therefore truth is not a special virtue.

Obj. 2: Further, to make known what belongs to oneself is an act of
truth as we understand it here. But this belongs to every virtue,
since every virtuous habit is made known by its own act. Therefore
truth is not a special virtue.

Obj. 3: Further, the truth of life is the truth whereby one lives
aright, and of which it is written (Isa. 38:3): "I beseech Thee . . .
remember how I have walked before Thee in truth, and with a perfect
heart." Now one lives aright by any virtue, as follows from the
definition of virtue given above (I-II, Q. 55, A. 4). Therefore truth
is not a special virtue.

Obj. 4: Further, truth seems to be the same as simplicity, since
hypocrisy is opposed to both. But simplicity is not a special virtue,
since it rectifies the intention, and that is required in every
virtue. Therefore neither is truth a special virtue.

_On the contrary,_ It is numbered together with other virtues (Ethic.
ii, 7).

_I answer that,_ The nature of human virtue consists in making a
man's deed good. Consequently whenever we find a special aspect of
goodness in human acts, it is necessary that man be disposed thereto
by a special virtue. And since according to Augustine (De Nat. Boni
iii) good consists in order, it follows that a special aspect of good
will be found where there is a special order. Now there is a special
order whereby our externals, whether words or deeds, are duly ordered
in relation to some thing, as sign to thing signified: