Lying by omission is a deliberate choice to hide or withhold some relevant information that would influence the decision process of another party. In other words: "I know you would probably take another decision if I told you what I know, but I won't tell you".

Some argue that by not communicating false information, one is indeed not lying. However, the consequences of lying by omission can be as dramatic as lying for the other party. I don't see this argument as being valid to make such a practice an ethical one (I would like to avoid semantic debates about the definition of lying).

In addition, some people claim that by explicitly disclosing that they may lie by omission, that is, warn the other party in advance, is enough to remain ethical. To me, this is akin to saying: "It's ok if I lie to you, because I warned you". I don't see how this can be considered ethical.

Is there any way I can fully trust someone who claims that lying by omission is acceptable? If that person is in an authority position, with responsibilities, is there any way they can justify this?

  • 1
    what is ethical seems a different question that evaluating trustworthiness. As for justifying the authority case, think security clearances.
    – MmmHmm
    Feb 19, 2017 at 22:28
  • 1
    Is there actually an ethical difference between lying by omission, lying by telling a misleading truth, and lying by saying the untruth? I don't think so.
    – gnasher729
    Feb 20, 2017 at 13:27
  • Any philosophical system that would say that it is always unethical to lie, even to save oneself from a violent physical threat, is deeply flawed... so yeah. Feb 20, 2017 at 20:31
  • Even for Kant, lying by omission, when it is a form of resisting undue authority is not lying, if it is clear you are objecting by not answering. Also, the level of detail to any truth is basically infinite, and our ability to describe is finite, so we are all continually lying by omission. It is unavoidable, so it cannot be absolutely wrong. Indicating how hard you are willing to work, and how hard you expect the questioner to work in uncovering unaddressed questions is just establishing the terms of engagement (unless you are lying about them.)
    – user9166
    Feb 20, 2017 at 20:36

2 Answers 2


One easy approach would be to argue that failing to lie by omission would cause harm.

One case where I think it would be very easy to justify this would be if the person in authority is incapable of properly conveying the information. If I may use the terminology of speach acts, one often comes across situations where it is not possible to cause the correct perlocutionary act while speaking the whole truth because the listener cannot fathom the desired act. We see this in child rearing, when dealing with difficult topics such as death. We see this in religion, trying to convey the beautiful certainty our particular religion offers. We see this in all sorts of aspects of life such as love (how many times have people refused to explain what being in love feels like because they know they will fail to capture it).

In many cases, if you omit content, it will lead the listener to go investigate on their own and arrive at a point where their own understanding is sufficient that you can finally tell them the truth. On the other hand, if you tell them before they are ready, they may interpret that truth wrongly, and then misuse it.

In short, the mere act of telling somebody a truth does not always cause them to hear a truth. In such situations, omission may lead them closer to the truth than voicing that truth.


There's a plethora of everyday situations that benefit or require different degrees of deception as the means to move forward. It's part of the social contract that most of us subscribe to. It's what the good Dr. will tell us when little Johnny is on life support and the only thing that's keeping him alive is, well, we don't know what's keeping him alive and neither does the good Dr. But at that point, when all rational and scientific alternatives have been eliminated and the only thing that will keep us going is the reassurance that we've decided that the person we love is not going to die. It's most likely a lie we will all tell ourselves at some point but it's far from being unethical, it's necessary.

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