There is good reason to think lying is always wrong. Lying is wrong on Kantian grounds: it treats the other person as a tool to one's ends rather than as an autonomous rational being, and the practice of lying would undercut itself if universalized. Lying is wrong on natural law grounds: it is clearly a perversion of the nature of assertoric speech, using speech for the opposite of its natural end of communicating truth. Lying is malevolent, except perhaps in outré cases: in lying, we act to bring it about that the other has a false belief, and it is surely intrinsically bad to have a false belief. Lying is wrong on personalist grounds: in making an assertion one solicits the other's trust, but in deliberately speaking falsely, one betrays that trust in the act of soliciting it. And lying is wrong on theological grounds: God is truth, and the Book of Revelation lists liars among the damned.
On the other hand, even those who are willing to agree that lying is always wrong are unlikely to think there is anything wrong with sticking one's hat out on a stick so that one's enemy might shoot at it while one sneaks away. It is hard enough to protect the innocent against unjust aggressors without lying (and, alas, sometimes impossible). But to do so without any deceit is nigh impossible.
But some people—even very smart people—do in fact consider lying and deceit to be the same thing. After all, in both cases, it seems, one is trying to do the same thing, namely to induce a false belief, and if so, then the malevolence argument would make deceit be wrong for one of the reasons that lying is.
I once found this very puzzling. And then a colleague gave me the beginning of an answer. In cases of deceit, one is trying to get the other to do something, rather than trying to get the other to believe something. I think this story can be filled out in a way that makes for a neat distinction between deceit and all but perhaps outr´ cases of lying (more on those later). On the face of it, one might argue that if I stick out my hat, my intention is to bring it about that
- my enemy will think I am under the hat, and will shoot, and the commotion will cover my escape.
But this argument is mistaken. What is essential is that the enemy should take herself to have evidence that I am under the hat. She does not have to believe that I am under the hat to shoot. She only needs to take herself to have more evidence for my being there than for my being in any other particular place. That is all that is needed to rationally justify her shooting under the hat. And her belief that she has this evidence is in fact a true belief—she indeed does have such evidence. Now, an epistemically less cautious enemy may actually form the belief that I am under the hat. But here I can apply double effect. She forms the false belief on the basis of the evidence. I intend her to have the evidence and to shoot. The evidence is sufficient to lead to her shooting. I do not have to intend her to form that false belief. I suppose things go better for me if she does, but I need only intend that
- my enemy will take herself to have more evidence for me to be under the hat than anywhere else, and will shoot, and the commotion will cover my escape.
The same can be said when I lay a false trail at a cross-roads when I am pursued by the enemy. I only intend what is needed for the accomplishment of my plan. Belief that I've taken road A, when I've taken road B, is not needed. All that's needed is that my enemy have strong evidence that I've taken road A, since having strong evidence that I've taken road A is sufficient to justify her following road A. There is no evil in her having such strong evidence. The evidence consists, after all, of a truth—the truth that there are footprints leading A-ward.
The principle of double effect can justify some cases of deception—I may foresee the other's forming a false belief, but I don't intend that belief formation, either as an end or as a means. And, typically, I don't even foresee that belief formation—I only foresee the possibility of it, since I do not know how epistemically cautious the other person will be. All that I intend is for the other person to have evidence for a false belief, and to act on that evidence.
Of course, in some cases of deceit, one is positively intending that the other have a false belief. For instance, a student plagiarist might desire not merely that her parents have evidence of her innocence, but that her parents positively believe her innocent. If she then manufactures evidence for her innocence with the intention that her parents believe her innocent, the above will be no excuse.
If this story is right, and if it is not to justify well-intentioned lies every bit as much as deceits, then there must be a crucial difference between how assertions function and how evidence functions. Assertions cannot simply be intended as yet another piece of evidence. For if they are, then in affirming a falsehood, we are not trying to induce any false belief in the other, but we are simply manufacturing misleading evidence. And, indeed, I do think assertions directly justify beliefs, in ways that are not merely evidential.
We can now go back to the reasons for believing lying to be wrong, and see if they apply to cases of deceit where one is not intending false belief but only misleading evidence. The Kantian "using" argument may not work (I used to think it would work, but I am not so clear on that). Maybe one is not circumventing the other's rationality, but only ensuring that the other act on unclear evidence. Nor is it clear that the practice of generating misleading evidence is not universalizable. Even if everybody who has good reason to deceive generates misleading evidence, there will be enough cases where non-misleading evidence is generated unconsciously that the evidence will still have some weight. Making footprints or putting a hat on a stick are not actions that have a natural end that is being circumvented here in the way in which lying circumvents the natural end of assertion. So the natural law argument against lying fails to show deception to be wrong. If the double effect considerations above are correct, the malevolence argument fails. The personalist argument also fails, because when we take something as evidence, rather than as testimony, trust in another person need not be involved. I do not trust persons to leave footprints leading to them—I have no right to feel betrayed if they leave footprints pointing in other directions. God is truth, but the cases of deceit that I have defended are not directly opposed to truth, since they do not involve an attempt to cause a false belief.
Final comment: Twice I mentioned that there could be outré cases of lying where there is no intention of causing false belief. These would be cases where one does not expect to be believed. There could, for instance, be cases where one knows that the other person is expecting one to lie, and so one says something false, in order to lead the other to true belief. I don't know if this is really a betrayal of trust since there is no trust. I don't know if people would count this as lying—it doesn't, for instance, meet the Catholic Catechism's definition of lying as a false assertion intended to deceive. But if one wishes to count this as a case of lying, it is a form of lying that may be significantly morally different from the others.