Primer

Over your first few years of life, you learned how to do a lot of things: how to speak, how to think, how to walk, how to grasp and manipulate objects, etc. But you learned most of these things implicitly—that is, without having words for what you were doing and how. For example, you learned many words before you knew the word “word,” and you learned how to put words together into sentences before you had the word “sentence” or words for the parts of speech (much less for the rules of grammar). Here’s another example: Many of you have probably never thought much about how to walk, but if you’ve ever had physical therapy to recover from an injury or taken a movement class as part of learning how to dance or to act, you may have learned to analyze the act of walking into component parts and this will have given you more control over the way you walk. Likewise, when athletes train, they often learn to analyze movements they learned as a child into simpler movements, and this process gives them finer grained control over their movements. It is possible to gain greater control of your thinking in the same way, by learning to analyzing the complex activity of thinking into the various mental acts that make it up. In this primer we’re going to focus on a part of our mental activity that looms large in our daily lives, in the sciences, and in philosophy: the activity of arguing. We will learn what an argument is, how to analyze an argument into its parts, and how to use this analysis to methodically assess an argument. In §1, I provide an overview of the whole process, and §2–5 deal in greater detail with different aspects of the process.

Propositions

Before we discuss arguments in earnest, it will be helpful to say a bit about propositions, which are the smaller units of thought from which arguments are composed. A proposition is the sort of thought that is capable of being true or false, believed or disbelieved, and asserted or denied. Such thoughts are asserted by declarative sentences. Here are some examples:

1. Healthy grass is green.

2. O. J. Simpson killed Nicole Brown.

3. Twice two is four.

4. Twice two is five.

5. Many diseases are caused by bacteria.

6. Stalin was evil.

7. Joe Biden is the 46th President of the United States.

8. Either a Republican or a Democrat will win the 2024 Presidential election.

9. The Senate should have convicted Donald Trump in both of his impeachment trials.

10. Hillary Clinton would have been an awful president.

The proposition is not the same thing as the sentence asserting it because the same thought can be asserted by different sentences. For example, here are several different ways of asserting Proposition 3 from the list above:

3a. Twice two is four.

3b. Two times two is four.

3c. 2 x 2 = 4

3d. Deux fois deux c'est quatre.

3e. 兩次兩次是四次。

Sentences 3a and 3b are two different ways of asserting the same proposition in English. 3c is a way of asserting it in mathematical notation, 3d is a way of asserting it in French, and 3e is a way of asserting it in Chinese.

Another reason why a proposition is not the same thing as a sentence, is that propositions can be asserted as parts of more complex sentences that include multiple propositions. For example, here’s a sentence that asserts both Propositions 9 and 10 from the list above: "Even though Hillary Clinton would have been an awful president, the Senate should have convicted Donald Trump at both of his impeachment trials."

Some of the propositions from the list above are uncontroversially true and others are uncontroversially false. I expect that everyone in the class will all agree that Propositions 1, 3, 5 and 7 are true and that Proposition 4 is false. We will probably disagree over some of the others—with some students thinking they’re true and others thinking they’re false.

Some of you may think that some of the propositions we may disagree over aren’t really the sort of things that can be true or false at all. In particular, some of you may think this about Propositions 6, 9, and 10, because these propositions express evaluations. Some people think that evaluations aren’t the sorts of things that can be true or false. But even if you think this, you’ll have noticed that many people believe or disbelieve each of these propositions (and many other evaluations) as though they were true or false, and they make arguments to try to convince other people that these propositions are true or falce. So, to understand their role in arguments you’ll have to treat them as the sort of thing that can be true or false.

How to Assess Arguments

(Or maybe this should be it's own overview article.) (There should definitely be separate articles (linked here) on Epistemic Status of Propositions, and on Assessing Different Types of Inference.)