Here’s a simple question: what is lying?
“Ah, well, that’s easy,” you might think. “Lying is telling an untruth.”
But this brief definition doesn’t quite get at the heart of the matter. For we might think it includes some things as lying which ought not to be so regarded, such as telling a fictional story, or making a joke, or even playing certain kinds of games. Further, it may exclude some things from qualifying which we want to say are lies. For example, if the teacher asks the class, “Did one of you draw that picture of me on the whiteboard?” and no one responds, no student told an untruth. However, supposing at least one of them is responsible and/or knows who did it, their silence most of us would count as lying to the teacher about their involvement. So, it appears this definition is both too broad (including things we don’t want) and too narrow (excluding things we do).
So, suppose you reconsider and reply: “Lying is deceiving others.”
This at least accounts for lying by omission, as in the case of the teacher. But this runs into a problem we’ve seen before: it includes things we do not really want to say are actual lies. For example, consider your favorite football team. They often come to the line of scrimmage attempting to disguise their defense, or on offense make a fake move before unleashing their real play, and so on. Are these all lies, all moral violations, and hence evil? It would seem not.
So, suppose you think for another moment and suggest this: “Lying is an attempt to have another person x believe P, when not-P is true, and x should have a reasonable expectation (or else a “right”) to receive the truth about P.”
Now this has some merit. In order to defeat a proposed definition, one will typically want to show it is either too broad or too narrow. Does this definition survive? Let’s test it against some of our examples: First, if we’re telling a fictional story, we get the right answer that we’re not lying, since x does not have a reasonable expectation that he will receive the truth about P. Making a joke is also excluded, as are games. There is, of course, the worry jokes or stories are taken too far—but we tend to agree it’s not in virtue of these being jokes and stories that they are lies. It also includes lying by omission.
It also provides what many of us take to be the “right” answer in some classic ethical quandaries. Consider the family hiding Jews in WWII Germany and the Nazis come by. They ask, “Are there any Jews here?” If you answer “no,” then you are lying and thereby violate a moral norm. If you answer “yes,” however, you are not protecting the innocent (at least not very effectively, anyway). While there are answers that vigorously defend the “yes” position, we typically want to say protection of the Jews by saying “no” is morally justified. But it also seems bizarre to claim lying is ever morally right or permissible. In fact, it’s a violation of the ninth commandment (Exodus 20:16)! But on this view, answering “no” is not lying. The Nazi does not have a reasonable expectation for the family to tell him the truth about the Jews, given that he intends to persecute, torture, experiment on, and ultimately kill them.
There is one worry here, and it’s about rationality. Suppose the Nazi thinks, “They know, or should know, that telling me an untruth about the presence of Jews will result in their incarceration or death, and the risk that I will check their home anyway is decent. Thus, the rational thing for them to do is to tell me the truth.” Here, it seems the Nazi has a reasonable expectation after all (is it really unreasonable, given the thought process?). But this is why I added “the right” portion above. Given that it’s a moral atrocity, if such people are hiding Jews, it’s because they have moral sensitivities (most likely); if that is the case, does he have the right to expect such people to move against these sensibilities and answer him, revealing the presence of the Jews? It seems not. The one committing a moral crime is not necessarily owed—or does not have the right to reasonably expect—the truth in a particular situation in which he is involved directly with moral evil.
And now we can apply this in the biblical narrative. In an ethics/moral philosophy course, we were once asked how many of us thought Rahab’s lie to cover for the pair of Jewish spies was justified, and how many thought it was not. The prof noticed my hand not going up for either, and I communicated I didn’t think it was a lie at all. We moved on for the sake of discussion, but I think it’s the right answer. It was not truth-telling, but as the enemies of God they did not satisfy what I am calling the reasonable expectation condition, and so should not have expected to hear the truth. Again, it must be noted that this condition deals with the rights one has to the truth in a given situation involving direct moral issues. I’ll leave it to others to decide whether or not telling people they look good when they don’t qualifies. J
 Here I am thinking of the game “Two Truths and a Lie,” where the winner is the one who convinces the others of the truth of the story when it is in fact false.
 Note also that if one protests that we could tell x “What I am about to tell you is absolutely true,” that it would be a lie. But this comports perfectly well with the definition given: in those circumstances, all being equal, x does have a reasonable expectation to be given the truth.