4.6: Validity’s Multiple Functions

I mentioned near the beginning of this chapter that arguments are multifunction tools in inquiry. Arguments aren’t always used directly to show the truth of some conclusion. As we’ve just seen, the concept of a valid argument can be used to tease out falsity in the premises. For instance, we might consider a claim that sounds pretty good and ask what follows from that claim deductively. What conclusion could we validly argue for on the basis of that claim? If we find that by deductively valid reasoning we can get from our claim that sounds pretty good to an absurd conclusion, then we have shown that our starting point, the claim that sounded pretty good, is false. This strategy is known as reductio ad absurdum, which is a handy bit of Latin for “reducing to absurdity.” We can use this strategy to test an idea for problems by considering what follows from that idea by valid argument and making sure it doesn’t lead to anything obviously false or absurd.

Reductio ad Absurdum:

To illustrate reductio ad adsurdum, let’s consider a view about the nature of morality that many people find attractive: moral relativism. According to moral relativism, there are no objective moral standards, rather morality is relative to groups depending on what is considered right in that group. When we consider what follows from moral relativism deductively, we wind up with some pretty unsavory results. The first premise in this argument is just a statement of moral relativism as a view about the nature of morality. From here, bad things start to happen.

1. If a society considers something morally good, then it is morally good (relative to that society).
2. Nazi Germany considered the extermination of Jewish people good.
3. The extermination of Jewish people was good (relative to Nazi Germany).

The argument here is valid. Its logical form is a minor variation on a valid pattern we examined above. If the premises are true, then the conclusion must be true. This means that if the conclusion is false, at least one of the premises must be false. Note that the conclusion here is not about what the Nazis considered to be good, it’s about what is good in the only sense that matters according to moral relativism. Since the conclusion of this argument is obviously false, not to mention horrible, and the second premise is a matter of historical fact, moral relativism must be false. Here we have reasoned validly from a view about the nature of morality that many people find attractive to a conclusion that is obviously absurdly false and horrible. A view about the nature of morality that has obviously and horribly bad logical consequences has got to be false. Moral relativism reduces to absurdity, reductio ad adsurdum. Before you get to comfortable with any view, consider what be validly inferred from that view and make sure it doesn’t lead to any absurdities. The strategy we’d just identified as reductio ad absurdum is a powerful tool for teasing out false premises in an argument.

Revealing Hidden Assumptions:

Another very helpful function of valid argumentation is as an aid to revealing hidden assumptions. In everyday life we don’t generally formulate formally valid arguments when we give reasons for what we believe. And often these unmentioned premises are where our biases hide. A good understanding of deductively validity can help us bring these hidden assumptions and biases to light. For example:

1. Every story I hear about politician X on Facebook says he is doing a terrible job.
2. So, Politician X is doing a terrible job.

This is not a valid argument as it stands. We would have a valid argument if we added a premise as follows.

1. Every story I hear about politician X on Facebook says he’s doing a terrible job
2. If every story I hear about politician X on Facebook says he’s doing a terrible job, then politician X is doing a terrible job.
3. So, Politician X is doing a terrible job.

Now we have a valid argument, but adding the premise required to generate a valid argument reveals a hidden assumption we have reason to doubt. Facebook uses AI and algorithms to customize your newsfeed in order to maximize engagement. It turns out that anger is very engaging. As a result, Facebook algorithms tend to feed you news stories that will stoke your anger. If you have a history of clicking and commenting on stories that say awful things about politician X or others of his political persuasion, Facebook will load your news feed with more articles that say awful things about politician X. The same goes for Google, YouTube and most search engines and social media platforms. The reason Facebook keeps showing you stories about what a terrible job politician X is doing isn’t that politician X is actually doing a terrible job. Rather it’s that the AI behind Facebook algorithms knows that stories like this will keep you glued to the platform, posting angry comments about politician X, and soaking in advertising that profits Facebook. So, formulating deductively valid arguments brings our assumptions to light where they can be scrutinized for truth or reasonableness. A good understanding of deductive validity can be very useful in identifying and addressing our usually unspoken assumptions and biases (well, perhaps in the example we just considered, the bias lies mainly in the AI driven algorithms employed by Facebook).

Clarity:

For reasons we just been discussing, a good understanding of deductive validity can help you clarify your own reasons and express them clearly to others. If you can recognize when an argument you find appealing has some gaps, your understanding of validity will guide you in filling in those gaps. Assuming the argument is a good one, you will then have a clearer understanding of it and be able to express your reason more clearly to others. Of course, as just discussed, if your argument is not so great, employing your understanding of validity to clarify the argument can alert you to this and perhaps guide you in formulating a better argument. All of this applies to understanding the arguments offered by others. When others formulate their reasons in incomplete, less than valid ways, your understanding of validity can guide you in identifying the questions you’d want to ask in reconstructing a more charitable complete version of your friend’s argument.

Charitable Interpretation:

A good understanding of deductive validity will help you formulate the best possible arguments for your view. It will also help you formulate and appreciate the best possible arguments for views you oppose. Formulating the best possible interpretation of an argument for opposing views is what we call “charitable interpretation.” In the dialectical spirit of cooperatively working towards truth and reasonableness, it is best to be charitable in filling out your reconstruction of another’s reasons. While helping to clarify arguments is a kindness, this is isn’t the entire point of charitable interpretation. Finding faults with bad arguments for a view you disagree with doesn’t really undermine that view, it just undermines the bad argument. If you have good reasons for rejecting a view, you should aim to identify the flaws in the best possible arguments for the view you think is wrong. Trying to make the opposing view sound outrageous or ridiculous will only lead you into straw man attacks (see discussion of this fallacy in the next chapter). The strongest argument you can offer against a view you oppose is not the argument that makes the view sound outrageous, but the argument that targets the best interpretation of the opposing view and the best possible arguments for it. Being a reasonable and effective critical thinker calls for charitable interpretation of opposing views and the arguments for them, not just out a sense of fair mindedness, good as that may be, but also in order to be the most effective critic of the view you oppose.

We’ve now characterized a few useful functions for deductive argumentation beyond merely trying to give reasons for thinking that something is true. While sound arguments, arguments that are both valid and have all true premises, provide good reasons for accepting their conclusions as true, valid argument isn’t only useful for directly getting at the truth. A good understanding of validity is useful for teasing out false assumptions, revealing hidden premises, clarifying reasoning, and charitably reconstructing the reasoning of others.

The path to understanding complex issues, clarifying or resolving reasonable disagreements, and ultimately towards truth and knowledge is usually not a straight paved sidewalk. Contrary to popular opinion, logic is not “linear”. It takes some skill to gauge the terrain, recognize the switchbacks, and stay on the trail. A good understanding of deductive validity is powerful guide.