Friday, March 17, 2023

Defining deceit

A plausible definition of deceit is an action aiming to get someone to believe something one takes to be false.

But I wonder if that’s right. Here are two possible counterexamples.

  1. Socratic conversation: One of my students believes some proposition p that I take to be false. Through Socratic questioning, I attempt to get the student to draw the natural conclusion q from p. Even if I take q to be false, it doesn’t seem I am deceiving my student.

  2. Mitigation of error: Suppose that Alice believes Bob to be culpable for some enormity. You know that Bob never committed the enormity, but you also know it’s hopeless to try to convince Alice of this. But you think you have some hope showing Alice that instead of her evidence supporting the claim that Bob is culpable for the enormity, it only supports the claim that Bob has inculpably committed enormity. You show this to Alice, in the hope that she will come to believe Bob to have innocently committed the enormity, even though that is also false.

In both cases, one is working along with the evidence available to one’s interlocutor. It seems that deception requires one to get someone to believe something true by means of hiding or masking the truth. And here there is no such thing going on. There is nothing underhanded. In both cases, for instance, it would be quite possible for the other party to know what one is really thinking about the case. I need not hide from the student that I disagree with q and you need not hide from Alice that you don’t think Bob committed the enormity at all.

We can add an underhandedness condition to the account of deceit, but I don’t exactly know what underhandedness is.

It is well-known that defining lying is tricky. It looks like defining deceit is also tricky.


Harrison Lee said...

Alex, This is really interesting. I'm wondering if it might help to say that deceit involves trying to make someone believe something false *rather than something true*. Neither of your counterexamples involve such an attempt, and examples involving this do seem deceitful to me. The implications of this definition would of course vary based on how narrow the scope of an attempt is, though, and there may be cases where one simply attempts to get someone to believe something false while foreseeing that this would prevent him from believing something true, or where one attempts to prevent someone from believing something which is true while merely foreseeing that this would involve making him believe something which is false. I'm not sure whether such cases should be considered deceptive.

Alexander R Pruss said...


Very interesting indeed!

Here's a weird case of a lie. I am training Bob how to be more self-confident for a job interview. Past experience with this employer suggests that one of the questions he will be asked is whether his French or his Spanish is better. Now, Bob is actually not sure about the answer to the question, so if he is asked the question, he will sound indecisive. But this particular employer does not like indecisive people, and doesn't care much whether Bob is better at French or at Spanish. I happen to know that Bob's French is slightly better than his Spanish. However, Bob won't believe me if I say that his French is better than his Spanish, because although he is undecided, he is inclining in favor of thinking his Spanish to be better. So if I tell him his French is better, he will just be even more indecisive. So I tell him that his Spanish is better in order to make him decisive.

Now, I am not trying to keep Bob from believing anything true. If I could get him to think his French is better, that would be great. But I am trying to keep Bob from suspending judgment and thereby seeming indecisive, and I don't much care which way I move him.

However, I am clearly lying. And while perhaps not all lies are deceitful (bald-faced lies are not deceitful, but I am not 100% sure they are lies), it seems like this one is a deceitful lie.