^[1]Most critical thinking textbooks tell students nothing about how to construct good arguments of their own. Their focus is on the identification and evaluation of other people’s arguments—as you would expect, since they are after all critical thinking textbooks.

Although teaching students how to evaluate arguments is the primary goal of critical thinking courses, such courses also provide the ideal context for the teaching of argument construction. Writing courses sometimes instruct students in how to write an argumentative essay, but they tend not to go into any detail about what differentiates a good argument from a bad one. By the middle of a critical thinking course, in contrast, students should have acquired some idea of what makes a good argument good, so they are well placed to be told how to construct one themselves. Although learning the difference between a good argument and a bad argument goes some way towards showing you how to construct good arguments of your own, it does not go all the way. Some explicit instruction is needed.

However, it is difficult to provide such instruction in a large lecture class. The best way to learn argument construction, once you have learned how to evaluate arguments, is to construct arguments and then have them evaluated either by your peers or by a tutor. How can you teach argument construction in a lecture? All that there is to say about it (given that the students already know how to evaluate arguments) can be conveyed in about five minutes.

Here is a method of teaching argument construction that I have developed to suit a teaching situation in which there are two one-hour lectures and one one-hour tutorial per week. The lecture class contains approximately two hundred students: each tutorial group contains between ten and twenty. One lecture and one tutorial are devoted entirely to argument construction. The lecture consists of a five-minute introductory spiel followed by an in-class exercise in which we construct an argument as a group. Then the students are given a homework assignment: a list of statements from which they are to choose one and construct the best argument they can for it. In the tutorial, their arguments will be presented to the class, and the class will make suggestions about how the argument could be improved.

The five-minute introduction

The introductory spiel begins by reminding the students of what constitutes a good argument, and then goes on to suggest the following method for constructing one:

1. Consider your conclusion. If it is a conclusion that you believe, think about why you believe it, and write those reasons down. If the conclusion is not one which you believe, think “What reasons might someone have for believing that conclusion?” and write those reasons down.
2. If you end up with several distinct sets of reasons, divide your reasons into related groups.
3. Focus on one reason or group of related reasons. Consider whether or not there are any unstated premises that need to be added before those reasons will support your conclusion. If there are, add those premises.
4. Consider whether or not your initial premises and unstated assumptions are plausible. Do they in turn need to be supported by additional premises to make them acceptable to your intended audience? Add as many such premises as you think are necessary. Now you have an argument.
5. Evaluate your argument as if it were someone else’s. Consider what objections to it might be raised by a reasonable and knowledgeable opponent. Are the premises plausible as they stand, or do they need further support? Do the premises provide enough support for the conclusion: if they were true, would they make the conclusion sufficiently likely? If not, adjust your argument accordingly. One way to test the amount of support the premises give the conclusion is to try to construct counterexamples: see if you can think of any situations in which the premises would all be true but the conclusion false. If you find any such counterexamples, then you should add premises, or adjust your premises, in such a way that the counterexamples are blocked, thus strengthening your argument.

The group exercise in constructing an argument

Having explained the method, I present the class with a claim for which we are going to construct arguments. It should be a claim that does not require any specialized knowledge to argue for, one that the students are likely to have thought about, and preferably one for which there are lots of different arguments. “God exists” works well. I invite the class to come up with reasons why a person might believe that God exists, and write all of their reasons up on the blackboard without comment. Here is a typical list.

• Most people believe that God exists.
• People have believed in God for a very long time.
• The Bible says so.
• How else could the world have come into existence?
• God talks to me inside my head.
• There are miraculous healings.
• People speak in tongues.
• I was brought up to believe that God exists.

If some of the reasons given seem to belong to the same argument, the students put them together, and then they choose a reason or set of reasons that we will turn into an argument. I ask them what premises need to be added before the reason(s) will provide strong support for the conclusion, whether these added premises are plausible, and whether the original reason or reasons is plausible. Often the premises require additional premises to support them. It is easiest to present this in the form of a diagram on the blackboard, the diagram method being one that the students have already learned while learning how to analyze and evaluate arguments.

On the following page is an example constructed in a recent critical thinking class (obviously, there are more premises that could be added).

The aim is to construct the best argument possible on the basis of the chosen premise or set of premises. Usually it will not be an absolutely watertight argument, and when it is as good as it seems to be getting, I sometimes ask the students to point out premises or links which are questionable.

Sometimes it turns out that nothing resembling a good argument can be constructed on the basis of the reason given. For example, there are no plausible premises which can be added which will make “I was brought up to believe that God exists” a good reason to believe that God exists: this is an explanation of why the person believes in God, rather than evidence supporting the claim that God exists. In such a case, or when we have successfully constructed an argument and still have more time, we go on to construct an argument based on one of the other reasons on the list.

The homework exercise

At the end of the lecture, the students are given a list of claims and asked to choose one of them and construct the best argument for it that they can. I tend to use somewhat controversial claims about issues that are currently in the news. Then the students bring their arguments along to the tutorial, and the class provides constructive feedback.

Tutors report that students have difficulty with the homework exercise, because by this stage they have been so schooled in how to detect fallacious arguments that they see the flaws in their own arguments before they even get as far as writing them down. This is all the more reason to persevere in teaching them this commonsense method of elaborating their actual reasons for belief into detailed and well-constructed arguments. It would be a pity if one of the effects of a critical thinking course were actually to prevent students from constructing good arguments of their own.^[2]