Are all forms of deception wrong?

just wondering.

including things like undercover work, for example, I recently found about the organization called live action and I’m a bit confused on the morality of pretending to be seeking abortions to expose planned parenthood members.

also, are lies always mortal sin? or does it depend on the content you’re lying about?

The worst lie is bearing false witness against someone as that could ruin their lives.

Lying about the size of your television is different.

What Nelka said is true-depending on intent, knowledge, etc; however, our God is Truth also…

Here are a couple of lines from scripture:

Proverbs 12:22

Lying lips are an abomination to the Lord, but those who act faithfully are his delight.

Proverbs 10:9

Whoever walks in integrity walks securely, but he who makes his ways crooked will be found out.

I don’t think I ever read anything about Christ teaching and leading others by deception. Nor do I agree with deceiving anyone for any reason. God will be the judge and deal with those that defile his word and his teachings.

Further, the balance of determining a “little lie” from a “big lie” is too difficult for me to keep up with. I just try not to lie at all. It’s easier.

I can’t accept that, for example, infiltrating a terrorist organization by deception, for the purposes of saving lives and preventing bombings, would be wrong. I’m also a big fan of Santa Claus, which for some is also an issue tied up with “deception.”

Agree. Here’s another place where common sense comes in.

I don’t believe that in the case of an undercover operative using deception, pretext and guise in order to infiltrate and gain evidence of an ongoing criminal activity would be wrong as the intent is to uncover the truth and stop the crime from continuing. If it’s used to entrap otherwise innocent people through appealing to their greed then I agree that would be sinful.


The family that hid Anne Frank saved her and her family from death by deceiving the Nazis.
No absolutist can convince me that it was wrong or “sinful.”


the PURPOSE of the deception makes the difference.


A very good definition of a lie that I heard was that a lie is denying the truth to someone who has a legitimate right to it. Not telling the Nazis at your door who are seeking to do very bad things with information you provide about the Jews hiding in your basement would not have been Lying. Not telling Mom that it was you that dented the car yeah lying…

people use that argument for abortion too, is the purpose is to save the mother’s life, it should be ok

Deception is commonly used by the military, intelligence assets and law enforcement. In the last case, the goal should not be entrapment but spreading incomplete or false information, for example, that may motivate the person of interest to do something that keeps a crime from happening or provides evidence that one did. Surveillance is part of this as well. A stakeout means the person in question may believe he is not being watched when he in fact is.

Deception in everyday life is a different matter. Deceiving people at work, or family members or friends results in complications down the road. Some things can remain private but honesty, using the right words at the right time, is best.


DISCLAIMER: The views and opinions expressed in these forums do not necessarily reflect those of Catholic Answers. For official apologetics resources please visit