is, not
directly forbidden by God or His Church, may become sinful for some
other reason well known to us.

We must not, however, doubt concerning the sinfulness or lawfulness of
everything we do; for that would be foolish and lead us to be
scrupulous. If we doubt at all we should have some good reason for
doubting, that is, for believing that the thing we are about to do is or
is not forbidden. When, therefore, we have such a doubt we must seek
information from those who can enlighten us on the subject, so that we
may act without the danger of sinning. It is our intention that makes
the act we perform sinful or not. Let me explain. Suppose during Lent a
person should mistake Friday for Thursday and should eat meat--that
person would not commit a real sin, because it is not a sin to eat meat
on an ordinary Thursday. He would commit what we call a material sin;
that is, his action would be a sin if he really knew what he was doing.
On the other hand, if the person, thinking it was Friday when it was
really Thursday, ate meat, knowing it to be forbidden, that person would
commit a mortal sin, because he intended to do so. Therefore, if what we
do is not known to be a sin while we do it, it is no sin for us and
cannot become a sin afterwards. But as soon as we know or learn that
what we did was wrong, it would be a sin if we did the same thing again.
In the same way, everything we do thinking it to be wrong or sinful is
wrong and sinful for us, though it may not be wrong for those who know
better. Again, it is sinful to judge others for doing wrong, because
they may not know that what they do is sinful. It would be better for us
to instruct than to blame them. The best we can do, therefore, is to
learn well all God's laws and the laws of His Church as they are taught
in the catechism, so that we may know when we are violating them or when
we are not, i.e., when we are sinning and when we are not.

*55 Q. Why is this sin called mortal?
A. This sin is called mortal because it deprives us of spiritual life,
which is sanctifying grace, and brings everlasting death and damnation
on the soul.

When the soul is sent to Hell it is dead forever, because never again
will it be able to do a single meritorious act.

*56 Q. How many things are necessary to make a sin mortal?
A. To make a sin mortal three things are necessary: a grievous matter,
sufficient reflection, and full consent of the will.

"Grievous matter." To steal is