e consideration of that principle,
according to Ps. 35:4, "He would not understand, that he might do
well": whereas sometimes it is due to the mind being more busy about
things which it loves more, so as to be hindered thereby from
considering this principle, according to Ps. 57:9, "Fire," i.e. of
concupiscence, "hath fallen on them and they shall not see the sun."
In either of these ways blindness of mind is a sin.

Reply Obj. 1: The blindness that excuses from sin is that which
arises from the natural defect of one who cannot see.

Reply Obj. 2: This argument considers the second kind of blindness
which is a punishment.

Reply Obj. 3: To understand the truth is, in itself, beloved by all;
and yet, accidentally it may be hateful to someone, in so far as a
man is hindered thereby from having what he loves yet more.
_______________________

SECOND ARTICLE [II-II, Q. 15, Art. 2]

Whether Dulness of Sense Is a Sin Distinct from Blindness of Mind?

Objection 1: It seems that dulness of sense is not a distinct sin
from blindness of mind. Because one thing has one contrary. Now
dulness is opposed to the gift of understanding, according to Gregory
(Moral. ii, 49); and so is blindness of mind, since understanding
denotes a principle of sight. Therefore dulness of sense is the same
as blindness of mind.

Obj. 2: Further, Gregory (Moral. xxxi, 45) in speaking of dulness
describes it as "dulness of sense in respect of understanding." Now
dulness of sense in respect of understanding seems to be the same as
a defect in understanding, which pertains to blindness of mind.
Therefore dulness of sense is the same as blindness of mind.

Obj. 3: Further, if they differ at all, it seems to be chiefly in the
fact that blindness of mind is voluntary, as stated above (A. 1),
while dulness of sense is a natural defect. But a natural defect is
not a sin: so that, accordingly, dulness of sense would not be a sin,
which is contrary to what Gregory says (Moral. xxxi, 45), where he
reckons it among the sins arising from gluttony.

_On the contrary,_ Different causes produce different effects. Now
Gregory says (Moral. xxxi, 45) that dulness of sense arises from
gluttony, and that blindness of mind arises from lust. Now these
others are different vices. Therefore those are different vices also.

_I answer that,_ Dull is opposed to sharp: and a thing is said to be
sharp because it can pierce; so that a thing is called dull through
being ob