The question “why lie if the truth would suffice” can be interpreted in at least three ways. One way is to see it as asking about the motivation to lie—this is an inquiry asking for an explanation. A second way is to see it as an inquiry into the weighing of the advantages and disadvantages of lying. The third way is to see it as a rhetorical question that states, under the guise of inquiry, that one should not lie if the truth would suffice.
Since a general discussion of this question would be rather abstract, I will focus on a specific example and use it as the basis for the discussion. Readers should, of course, construct their own examples using their favorite lie from those they disagree with. I will use Trump’s response to the Democrats’ Green New Deal as my example.
In 2019 the Democrats proposed a Green New Deal aimed at addressing climate change and economic issues. As with any proposal, it has problems and rational criticisms can be raised against it. Trump asserted that the Democrats intend “to permanently eliminate all Planes, Cars, Cows, Oil, Gas & the Military – even if no other country would do the same.” While there are some Democrats who would endorse doing all of that, the Democrats as a party do not intend to do any of that. Looked at rationally, it would seem to make no sense to lie about the Green New Deal. If it is bad enough to reject on its own defects, lies would not be needed. If one must lie to attack it, this suggests that the person has no actual arguments against it—otherwise they would just point out the real defects. To use an analogy, if a prosecutor engages in lies to try to convict a person, this suggests that that they have no case against them—otherwise they would rely on real evidence. So, why would Trump lie if the truth would suffice to show the Green New Deal is a terrible plan?
The question of why Trump (or anyone else) lies when the truth would suffice is a matter for psychology, not philosophy. So, I will leave that question to others. This leaves me with the question about the advantages and disadvantages of lying as well as the rhetorical question.
The lie about the Green New Deal is a good example of hyperbole and a straw man. Trump himself claims to use the tactic of “truthful hyperbole”. Hyperbole is a rhetorical device in which one makes use of extravagant overstatement—such as claiming that the Democrats plan to permanently eliminate all cows. The reason hyperbole is not simply called lying is that it is a specific sort of untruth (an exaggeration) and it does have some foundation in truth. That is, hyperbole involves inflating or exaggerating something real rather than making something up entirely. The Green New Deal is aimed at making America carbon neutral and this would impact cars, cows, planes, oil, gas and the military. The extravagant exaggeration is that the proposal would eliminate all of them permanently. This would be as if someone proposes cutting back on dessert and Trump said the person plans to eliminate all meals permanently. Since hyperbole is simply rhetoric, it has no logical force—it does not prove (or disprove) anything. It can, however, have psychological force—it can make people feel a certain way so they believe a claim.
Hyperbole is often used in conjunction with the Straw Man fallacy. The Straw Man fallacy is committed when a person simply ignores a person’s actual position and substitutes a distorted, exaggerated or misrepresented version of that position. This sort of “reasoning” has the following pattern:
1. Person A has position X.
2. Person B presents position Y (which is a distorted version of X).
3. Person B attacks position Y.
4. Therefore X is false/incorrect/flawed.
This sort of “reasoning” is fallacious because attacking a distorted version of a position simply does not constitute an attack on the position itself. One might as well expect an attack on a poor drawing of a person to hurt the person.
Like hyperbole, the Straw Man fallacy is not based on a simple lie: it involves an exaggeration or distortion of something real. In the case of Trump and the Green New Deal, his “reasoning” is that the Green New Deal should be rejected because his hyperbolic straw man version is terrible. Since this is a fallacy, his “reasons” do not support his claim. It is, as always, important to note that Trump could be right that the Green New Deal is a bad idea—to infer that a fallacy must have a false conclusion is itself a fallacy (the fallacy fallacy).
While hyperbole has no logical force and a straw man is a fallacy, there are advantages to using them in the place of the truth. One advantage is that using them is easier than coming up with actual reasons. Criticizing the Green New Deal for what it is requires knowing what it is and considering the possible defects—this takes time and effort. Tweeting out a straw man takes mere seconds.
The second advantage is that hyperbole and straw men often work—and generally work better than the truth. In the case of complex matters, people rarely bother to do their homework and hence often do not know that a straw man is a straw man. For example, I have interacted with people who seem to honestly think that the Democrats plan to eliminate planes and cars entirely. Since this is a bad idea, they reject it—not realizing that is not the actual Green New Deal. The obvious defense against this is to do the work to know the facts. While this can take time and effort, if a person has the time to rant on Facebook or Twitter about the matter, they have the time to do some basic research. If not, their ignorance should command them to remain silent. Yes, they still have the right of free expression—I am not advocating that they be silenced.
As far as working better than the truth, a well-crafted hyperbole or straw man appeals to the target’s fears, anger or hope—they are thus motivated to believe to a degree that the truth would not match. People generally find rational argumentation dull and unmoving, especially when it is about complex matters. So, if Trump did lay out in detail the real problems with the Green New Deal, complete with supporting data and graphs, he would simply bore most people and they would tune out before he got to his conclusion. By using a straw man, he better achieves his goal of getting people to reject the Green New Deal. This does allow for a pragmatic argument for lying because the truth will not suffice.
If telling the truth would not suffice to convince people of a claim, then there is the obvious pragmatic argument that if lying would do the job, then it should be used. For example, if going into an honest assessment of the Green New Deal would merely bore people and lying would get the job done, then Trump should lie if he wants to achieve his goal. This does, however, raise some obvious moral concerns.
If the reason the truth would not suffice is because it does not logically support the person’s claim, then it would be immoral to lie. To use a non-political example, if you would not invest in my new fake company iScam if you knew it was a scam, getting you to invest in it by lying would be wrong. So, if the New Green Deal could not be refuted by the truth, Trump’s lies about it would clearly be immoral. To use an analogy, it would be like someone lying to get people to reject the measles vaccine. So, one should not lie if the truth would suffice.
But, what about cases in which the truth would logically support a claim, but the truth would not persuade people to accept the claim? Going back to the Green New Deal example, suppose that it is terrible but that explaining its defects would simply bore people and they would tune out and remain unpersuaded. But, a straw man version of the Green New Deal would persuade many people to reject this (for the sake of the discussion) terrible plan? From a utilitarian standpoint, the lie could be morally justified—if the good of lying outweighed the harms, then it would be the right thing to do. To use an analogy, suppose you were trying to convince a friend to not start a foolish and ineffective diet. You have all sorts of scientific data and good arguments, but you know your friend is bored by data and is largely immune to logic. So, telling them the truth would mean that they would go on the diet and end up suffering some health issues. But, if you exaggerate the harms dramatically, your friend will be scared and not try the diet. In such a case, the straw man argument would seem to be morally justified—you are exaggerating to protect your friend from a bad choice.
While this might seem to justify the general use of hyperbole and the straw man, ironically it only justifies their use when the truth does suffice logically but does not suffice in terms of persuasive power. That is, the fallacy is only justified as a persuasive device when there are non-fallacious arguments that would establish the same conclusion.