a sin. Now, if you steal only a pin the
act of stealing in that case could not be a mortal sin, because the
"matter," namely, the stealing of an ordinary pin, is not grievous. But
suppose it was a diamond pin of great value, then it would surely be
"grievous matter." "Sufficient reflection," that is, you must know what
you are doing at the time you do it. For example, suppose while you
stole the diamond pin you thought you were stealing a pin with a small
piece of glass, of little value, you would not have sufficient
reflection and would not commit a mortal sin till you found out that
what you had stolen was a valuable diamond; if you continued to keep it
after learning your mistake, you would surely commit a mortal sin. "Full
consent." Suppose you were shooting at a target and accidentally killed
a man: you would not have the sin of murder, because you did not will or
wish to kill a man.

Therefore three things are necessary that your act may be a mortal sin:
(1) The act you do must be bad, and sufficiently important; (2) You must
reflect that you are doing it, and know that it is wrong; (3) You must
do it freely, deliberately, and willfully.

57 Q. What is venial sin?
A. Venial sin is a slight offense against the law of God in matters of
less importance, or in matters of great importance it is an offense
committed without sufficient reflection or full consent of the will.

"Slight," that is, a small offense or fault; called "venial," not
because it is not a sin, but because God pardons it more willingly or
easily than He does a mortal sin. "Less importance," like stealing an
ordinary, common pin. "Great importance," like stealing a diamond pin.
Without "reflection" or "consent," when you did not know it was a
diamond and did not intend to steal a diamond.

*58 Q. Which are the effects of venial sin?
A. The effects of venial sin are the lessening of the love of God in our
heart, the making us less worthy of His help, and the weakening of the
power to resist mortal sin.

"Lessening of the love," because it lessens grace, and grace increases
the love of God in us. It displeases God, and though we do not offend
Him very greatly, we still offend Him. "Weakening of the power to
resist." If a man is wounded, it will be easier to kill him than if he
is in perfect health. So mortal sin will more easily kill a soul already
weakened by the wounds of venial sin.

59 Q. Which are the chief sources of sin?
A. The chief sour