To all:
Many people hear the word "deception,"
and automatically think it is always bad.
In fact, you look in the dictionary and find a bad definition.
There is good deception and bad deception.
While Wikipedia appears to also color the word "deception" as bad, it does offer us a glimpse into the truth behind this word.
"Deception is an act or statement which misleads, hides the truth, or promotes a belief, concept, or idea that is not true."
Deception - Wikipedia
The words in green above is a good form of deception.
The words in red above is a bad form of deception.
If deception was always bad, then we must conclude that the two spies that Joshua sent were bad. This is simply not the case.
In other words, good deception is merely hiding the truth,
but not lying or being untruthful.
Scripture says it is to the glory of God to conceal a matter.
"
It is the glory of God to conceal a thing: but the honour of kings
is to search out a matter." (Proverbs 25:2).
Jesus did not openly declare that He was God. Jesus even evaded this truth when the Jews wanted to stone Him by His quoting of Scripture about how "ye are gods..." (John 10:4) (Psalms 82:6). Jesus was not giving them the whole truth here. He was evading it so as to protect His mission. As another poster pointed out, Jesus said He was not going to go to a certain party, but He went in secret. This again, is a form of hiding or a form of good deception, because they thought He was going but they did not know He was going in secret. Jesus spoke of His resurrection, but His disciples did not get it at first. God was sort of in a way hiding this truth from them until after Jesus had risen. For Jesus could have sat down and fully explained it to them. In Joshua 8, the Lord gave Joshua a battle tactic that would deceive the enemy. This was a good form of deception. No untruth was used in the deception. No lies were spoken and no illusion that was untrue was put forth.
Bad deception is something that promotes an idea that is entirely not true. This falls into the realm of something that is a lie and is completely untrue. It would be like a man named Rick saying there are purple cats that breath fire, or green cats that can fly. This would be like when the devil told Eve that she would not die if she ate of the tree that God forbid her and Adam to eat of (See: Genesis 3). A lie is saying something that is entirely not true or doing something that is totally contrary to any kind of truth. I believe that when King David acted insane, this was a form of lying by a form of performance. David was not really insane. So this was a lie. It was a bad deception on David's part. There is no way to find him innocent in this regards unless David was literally insane (Which seems highly unlikely).