So far I have defined arguments in terms of premises and conclusions, where the premises are supposed to provide a reason (support, evidence) for accepting the conclusion. Many times the goal of giving an argument is simply to establish that the conclusion is true. For example, when I am trying to convince someone that obesity rates are rising in the U.S. I may cite evidence such as studies from the Center for Disease Control (CDC) and the National Institute of Health (NIH). The studies I cite would function as premises for the conclusion that obesity rates are rising. For example:
We know that obesity is on the rise in the U.S. because multiple studies carried out by the CDC and NIH have consistently shown a rise in obesity over the last four decades.
We could put this simple argument into standard form like this:
1. Multiple studies by the CDC and NIH have consistently shown a rise in obesity over the last four decades.
2. Therefore, obesity is on the rise in the U.S.
The standard form argument clearly distinguishes the premise from the conclusion and shows how the conclusion is supposed to be supported by the evidence offered in the premise. Again, the goal of this simple argument would be to convince someone that the conclusion is true. However, sometimes we already know that a statement or claim is true and we are trying to establish why it is true rather than that it is true. An argument that attempts to show why its conclusion is true is an explanation. Contrast the previous example with the following:
The reason that the rate of obesity is on the rise in the U.S. is that the foods we most often consume over the past four decades have increasingly contained high levels of sugar and low levels of dietary fiber. Since eating foods high in sugar and low in fiber triggers the insulin system to start storing those calories as fat, it follows that people who consume foods high in sugar and low in fiber will tend to store more of the calories consumed as fat.
This passage gives an explanation for why obesity is on the rise in the U.S. Unlike the earlier example, here it is taken for granted that obesity is on the rise in the U.S. That is the claim whose truth we are trying to explain. We can put the obesity explanation into standard form just like any other argument. In order to do this, I will make some paraphrases of the premises and conclusion of the argument (for more on how to do this, see section 1.5 below).
1. Over the past four decades, Americans have increasingly consumed foods high in sugar and low in fiber.
2. Consuming foods high in sugar and low in fat triggers the insulin system to start storing those calories as fat.
3. When people store more calories as fat, they tend to become obese.
4. Therefore, the rate of obesity is on the rise in the U.S.
Notice that in this explanation the premises (1-3) attempt to give a reason for why the conclusion is true, rather than a reason for thinking that the conclusion is true. That is, in an explanation we assume that what we are trying to explain (i.e., the conclusion) is true. In this case, the premises are supposed to show why we should expect or predict that the conclusion is true. Explanations often give us an understanding of why the conclusion is true. We can think of explanations as a type of argument, we just have to distinguish two different types of argument: those that attempt to establish that their conclusion is true (arguments), and those that attempt to establish why their conclusion is true (explanations).
Which of the following is an explanation and which is an argument? Identify the main conclusion of each argument or explanation. (Remember if the premise(s) seems to be establishing that the conclusion is true, it is an argument, but if the premise(s) seems to be establishing why the conclusion is true, it is an explanation.)
1. Wanda rode the bus today because her car was in the shop.
2. Since Wanda doesn’t have enough money in her bank account, she has not yet picked up her car from the shop.
3. Either Bob or Henry rode the bus to work today. But it wasn’t Henry because I saw him riding his bike to work. Therefore, it was Bob.
4. It can’t be snowing right now since it only snows when it is 32 degrees or below and right now it is 40 degrees.
5. The reason some people with schizophrenia hear voices in their head is that the cognitive mechanism that monitors their own self-talk is malfunctioning and they attribute their own self-talk to some external source.
6. Fracking should be allowed because, although it does involve some environmental risk, it reduces our dependence on foreign oil and there is much greater harm to the environment due to foreign oil drilling than there is due to fracking.
7. Wanda could not have ridden the bus today because today is a city-wide holiday and the bus service is not operating.
8. The Tigers lost their star pitcher due to injury over the weekend, therefore the Tigers will not win their game against the Pirates.
9. No one living in Pompeii could have escaped before the lava from Mt. Vesuvius hit. The reason is simple: the lava was flowing too fast and there was nowhere to go to escape it in time.
10.The reason people’s allergies worsen when they move to Cincinnati is that the pollen count in Cincinnati is higher than almost anywhere else in the surrounding area.