Certainly God "knows all things." First, because He is infinitely wise,
and if He were ignorant of anything He would not be so. Secondly,
because He is everywhere and sees and hears all. Darkness does not hide
from His view, nor noise prevent Him from hearing. How could we sin if
we thought of this! God is just here, looking at me and listening to me.
Would I do what I am going to do now if I knew my parents, relatives,
and friends were watching me? Would I like them to know that I am
thinking about things sinful, and preparing to do shameful acts? No! Why
then should I feel ashamed to let God see and know of this wicked
thought or action? They might know it and yet be unable to harm me, but
He, all-powerful, could destroy me instantly. Nay, more; not only will
God see and know this evil deed or thought; but, by His gift, the
Blessed Mother, the angels and saints will know of it and be ashamed of
it before God, and, most of all, my guardian angel will deplore it.
Besides, this sin will be revealed to the whole world on the last day,
and my friends, relatives, and neighbors will know that I was guilty of
it.

19 Q. Can God do all things?
A. God can do all things, and nothing is hard or impossible to Him.

20 Q. Is God just, holy, and merciful?
A. God is all just, all holy, all merciful, as He is infinitely perfect.

"All just"--that is, most just. "Just" means to give to everyone what
belongs to him--to reward if it is merited or to punish if it is
deserved. "Holy"--that is, good. "Merciful" means compassionate,
forgiving, less exacting than severe justice demands. In a court a just
judge is one who listens patiently to all the arguments for and against