How to map arguments from a text

To analyze something is to break it down into its constituent parts, and to analyze an argument is to break it down into its premises and conclusion. I will focus on analyzing arguments presented by other people in written form. Of course, one hears arguments in conversations all the time, and the process by which one analyses them is essentially the same as with written arguments, but it is more difficult because one does not have a “fixed target” which one can take the time to study at one’s own pace. One also can analyze one’s own arguments as well as those offered by other people, but in doing so it is important to achieve a certain critical distance from the argument, and this is best achieved by writing it out and then treating it as though it were written by someone else.

Finding the arguments

When trying to analyze the arguments in a given text the first step is to identify which passages contain arguments. You need to single out those stretches of text in which one or more propositions are cited as a reason to believe another. There are many ways in English to indicate that one proposition is being offered in support of another. For example, we might say “I should respect her, because she’s my mother,” or “She’s my mother, so I should respect her,” “I should respect her, for she’s my mother, or “She’s my mother; therefore, I should respect her.” In all of these cases, “She’s my mother” is being offered as a premise in support of the conclusion “I should respect her.”

Some of the ways this argument might be expressed:

• I should respect her, because she’s my mother.
• She’s my mother, so I should respect her.
• I should respect her, for she’s my mother.
• She’s my mother. Therefore, I should respect her.
• I should respect her; she is my mother after all.

Words like “so,” “therefore,” “thus,” “hence,” and “consequently” are often used to introduce conclusions; and words like “because,” “for,” and “since” often introduce premises. “Surely,” “certainly,” “no doubt,” and other words that signal confidence in what one’s about to say are also often used to introduce premises. Words of the sorts we’ve been discussing are sometimes called inferential particles. Looking out for these particles can help you to identify arguments and adding particles to your own writing is a good way to convey the structure of your own arguments to readers. However, all of these particles also have other uses in English, and people sometimes argue without using particles at all.

Premises and conclusions can be indicated in other ways. For example, in some contexts, one can indicate that a proposition is a conclusion by saying that it “must” or “has to be” the case, but like particles, these words have other uses as well. Or someone could be very explicit and say, “I conclude that I have to respect her, on the basis of the premise that she’s my mother.” Or, swinging from one extreme to the other, he might express the same argument by saying simply: “She’s my mother. I should respect her,” or “I should respect her. She’s my mother.” And, in most contexts, if someone said this, you would recognize that he probably meant one proposition to support the other, and you would be able to tell which was which, because you understand enough about the relations between the propositions to figure out what the author probably intends. Again, sometimes premises or conclusions can be expressed in the form of rhetorical questions: “Shouldn’t I respect her? After all, isn’t she my mother?” There is a wide variety of ways in which premises and conclusions can be expressed, and in which we are able to recognize that this is what is being done.

Identifying the Conclusion and All the Premises

Once you are confident that you have found an argument, you need to identify its premises and conclusion. In order to recognize that a passage contains an argument in the first place, you must have already noticed that at least one proposition is intended either to support or to be supported by another. Thus, you will have already identified either a conclusion or a premise. Now you need to identify any remaining premises or conclusions that there may be. In doing this, keep in mind that they may be introduced with inferential particles, but they needn’t be.

The argument may be presented in any order. For example, each of the sentences expresses the same argument as the map on the right.

Map 9:

(i) Alcohol should be illegal, because it’s a drug and all drugs should be illegal.

(ii) Alcohol is a drug, and all drugs should be illegal, so alcohol should be.

(iii) All drugs should be illegal, so alcohol should be, since it’s a drug.

In (i), the conclusion is written first, followed by the two premises; in (ii) the conclusion is written after the premises; and in (iii), it is placed in between them.

To ensure that you have found all of the premises and the conclusion, read through the passage carefully, focusing separately on each proposition—each claim that could be expressed as a separate sentence (however it is actually formulated in the passage as written). Then ask yourself why the proposition is there. Is it intended as a part of the argument or as some sort of aside? If it is part of the argument, then what role is it playing: is it meant to be supporting some conclusion, or to be supported by some other proposition?

If you are having trouble figuring out whether one proposition is intended to support another or to be supported by it, it can help to ask yourself which proposition is more obviously true. In arguments, we try to establish propositions that we are less sure of by inferring them from ones that we are more sure of.

Implicit Premises

You may have noticed that there’s something unnatural about the three sentences we looked at above, expressing the argument that alcohol should be illegal. It is unlikely that anyone making this argument would state it so long-windedly. More likely he’d simply say: (iv) “Alcohol should be illegal because it’s a drug” or perhaps (v) “Alcohol should be illegal because all drugs should be.” Both of these ways of stating the argument omit one of the premises. People often do this when they think it is obvious what premise would be needed to complete their argument and when they think the person they’re speaking with will agree to that premise. If one maps these arguments as written, here’s what one would get:

Map 9a & 9b:

Inferences B and C are non-sequiturs, whereas Inference A (in Map 9) is a deduction. Moreover, it is obvious what premise you could need to add to Argument B (or Argument C) to make a very strong inference (namely, Inference A).

We encountered another example of this phenomenon in map 8, above. Here is that map again:

Map 8:

Some ways this argument might be expressed:

• I should respect her, because she’s my mother.
• She’s my mother, so I should respect her.
• I should respect her, for she’s my mother.
• She’s my mother. Therefore, I should respect her.
• I should respect her; she is my mother after all.

This map is a map of the argument expressed in different ways by each of the sentences on the right. But the argument is clearly incomplete as written. Inference A is a non-sequitur, which makes Argument A worthless. But if someone said any of the sentences on the right, you would recognize that he was giving you some reason to believe Proposition 1. This is because there’s another premise, which is plausible that when combined with Proposition 2 would make for a stronger argument as follows.

Map 8a:

In this map, Proposition 3 is enclosed in brackets to indicate that it isn’t stated in the passage we are analyzing and that we have added it ourselves, because we think that the author of the passage intended us to assume it as a premise of the argument. Such unstated premises are called implicit.

When analyzing an argument, it is important to make any implicit premises explicit—that is, to state them. This is necessary because, when you assess the argument, you will need to assess all of the premises to determine how strong the argument is. Some arguments appear to be stronger than they are because their weakest premises are left implicit.

Not every unstated belief held by a person making an argument is an implicit premise of that argument, often not even if it is relevant to the subject of the argument. We can probably imagine all sorts of reasons that the person making this argument has for believing that people should respect their mothers. Still, none of these reasons count as implicit premises of the argument mapped above. Something is an implicit premise only if it needs to be added to an argument to prevent one of its inferences from being a non-sequitur, and if it is likely that the person making the argument intended you to assume it.

Thus, the process of finding implicit premises is closely related to the process of assessing the inference. Once you have identified the stated premises and the conclusion, you may notice that the conclusion does not follow from the premises. At this point, there are two possibilities: either the inference is a non-sequitur; or there is an implicit premise, which does make the conclusion follow from the premises. You need to use your judgment as to which is the case. Is it more likely that the author of the argument made a non-sequitur or that he left one of his premises unstated? People rarely make arguments that include obvious non-sequiturs, so in such cases, it is likely that there is an implicit premise that the author intended you to assume. There are some subtle situations where it is difficult to determine whether an argument is bad or whether there is some implicit premise, and there are cases where it is hard to tell which of several different premises might be implicit. But more often than not, it is very clear when someone is relying on an implicit premise and what that premise is.

Multi-Step Arguments and Multiple Arguments to the Same Conclusion

There are multi-step arguments, where a premise of one argument is supported by a further argument. You need to be on the lookout for this sort of structure when mapping. Here’s an example:

Jane’s visit must have been over a weekend, since she spent two full days here, and she wouldn’t have been able to do so during the week. But Rob wasn’t in town, so the visit had to be on the first weekend in July, since that’s the only one when he wasn’t here.

Map 10:

The first sentence of the passage gives us Argument A, with Proposition 1 as its conclusion, and the second sentence then gives us the remaining propositions in Argument B.

It is not uncommon in such multi-step arguments for some of the propositions to be left implicit. For example, here’s another way in which someone might express the same argument mapped above.

Jane wouldn’t have been able to spend two whole days here during the week. But the only weekend when Rob was out of town was the first one in July, so her visit must have been over that weekend.

Here Propositions 1, 2, and 4 (from Map 10) are left implicit, but it is reasonably clear that the author of the passage intended the argument expressed by that map.

Distinguishing Arguments from Explanations

Consider the following passage and the map:

The sun is hot, because it is a ball of gases undergoing nuclear fusion, and nuclear fusion releases a great deal of heat.

The use of the particle “because” may lead us to interpret this as an argument, along the lines illustrated in the map. And if we knew Propositions 2 and 3, they would in fact give us a reason to believe Proposition 1. However, it is hard to imagine a situation in which someone would know Propositions 2 and 3 without already knowing Proposition 1, so it is unlikely that anyone would ever make this argument. The more natural way to interpret this passage is as giving us an explanation of Proposition 1.

An argument gives one a reason to believe that its conclusion is true, whereas an explanation cites the causes of a phenomenon. The gear-shaped inference symbol indicates that map 11 contains an explanation, rather than an argument.

Often when we’re trying to reach conclusions about things in the future, we use premises that are also causes. For example, we might conclude that it’s about the rain by noticing that there are dark clouds and that such clouds cause rain. But when we’re not reasoning about the future, we usually need to know that a proposition is true, before we try to discover its causes. That’s certainly the case in the passage above. We first know that the sun is hot, and then we try to discover the causes that explain why it is.

You can usually tell from context (and sometimes from the nuances of how inferential particles are used) whether a passage is meant to explain a proposition or to argue for it. If you’re unsure, it can help to ask yourself what question the passage is answering about the relevant proposition. If it’s an argument, it will be answering the question “How do you know it?” (or “What reason do you have for believing it?”). If it is an explanation, it will be answering the question “What caused it?”.

It is very easy to confuse an explanation for an argument when what is being explained is a person’s beliefs or actions. It is possible to think of a person’s actions or beliefs as effects and to try to explain them, often by citing biographical facts. Suppose that Charlie spanks his children, and we ask ourselves why he does this. Here are two answers we might come up with:

(i) Charlie spanks his children because he was spanked by his father.

(ii) Charlie spanks his children because he thinks it is the most effective way to discipline them.

Notice that (i) gives us an explanation of Charlie’s behavior, by citing things in Charlie’s past that might cause him to behave as he does, but it doesn’t give us Charlie’s reasons for acting in this way. By contrast, (ii) indicates what Charlie’s reasons might be.

Now consider another example that concerns a belief rather than an action. Suppose that Dana believes that it is wrong to eat meat, and we ask why she believes this. Here are two answers we might get.

(i) Dana’s parents believed that it is wrong to eat meat.

(ii) Eating meat causes suffering.

We can map these two answers as follows:

Map 13 of (ii):

Notice that (i) explains Dana’s belief by citing a factor in her biography that caused her to come to this belief, but it doesn’t give Dana any reason for believing as she does. It doesn’t help Dana or us to tell whether her belief is true. By contrast, (ii) gives something that might be Dana’s reason for believing as she does. It gives an argument that the belief is true.

Explanations of our actions or beliefs treat these behaviors and beliefs as things that just happen to us. But our beliefs and actions don’t just happen to us. You are responsible for the things you do and for the things you believe. This is why you need to think about the reasons you have for your beliefs and actions, and why you need to think about and evaluate other people’s reasons as well when judging them. Confusing explanations of beliefs (or behaviors) with arguments for them can obscure these reasons.

Example of a Complex Map

As an example of a more complex map than we’ve looked at so far. Here’s a brief passage, followed by a map of all the arguments it contains.

The laws prohibiting cannabis use should be repealed. They’re illegitimate in the first place, because the only proper basis for outlawing an activity is that it violates someone else’s rights, and you’re not violating anyone’s rights if you smoke a joint. Anyway, cannabis is way less dangerous than substances that it’s legal to buy and use. Tobacco causes cancer, whereas cannabis is being researched as a potential cancer cure! No one’s heard of a “cannabis overdose,” but it’s easy to kill yourself by overdosing on ibuprofen, which you can buy over the counter, and people die every year of alcohol poisoning. Some studies show that there are risks to driving under the influence of cannabis, but a stoned driver is way safer than a drunk driver. Yet people are allowed to go into any supermarket and buy a bottle of wine without being harassed by the cops, and our government is spending untold sums arresting people who buy or sell pot. Even people opposed to cannabis use should be able to see that this money is wasted, since it’s not stopping anyone from smoking up. And, by the way, white people smoke up every bit as much as anyone else, but somehow the majority of people arrested for cannabis-related offenses are black or Latino, which shows how racist the law is in practice. Instead of throwing away money on half-assed, racist enforcement of these illegitimate laws, the government could be making money on weed, by legalizing it and taxing it. That’s what Colorado did, and their tax revenues are way up, so we know it works. Crime and poverty rates also went down in Colorado, so if we want to make the rest of the country safe and rich, we might try following their example.

Map 14 (click for expanded view):