By Matthew Van Cleave

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).

Do Quiz 2c before moving further in the course.

Modifié le: vendredi 24 juillet 2020, 13:39