3.1 What is an argument?
Both logic and critical thinking centrally involve the analysis and assessment of arguments.
“Argument” is a word that has multiple distinct meanings, so it is important to be clear from the
start about the sense of the word that is relevant to the study of logic. In one sense of the word,
an argument is a heated exchange of differing views as in the following:
Sally: Abortion is morally wrong and those who think otherwise are seeking to justify murder!
Bob: Abortion is not morally wrong and those who think so are right-wing bigots who are
seeking to impose their narrow-minded views on all the rest of us!
Sally and Bob are having an argument in this exchange. That is, they are each expressing
conflicting views in a heated manner. However, that is not the sense of “argument” with which
logic is concerned. Logic concerns a different sense of the word “argument.” An argument, in
this sense, is a reason for thinking that a statement, claim or idea is true. For example:
Sally: Abortion is morally wrong because it is wrong to take the life of an innocent human being,
and a fetus is an innocent human being. In this example Sally has given an argument against
the moral permissibility of abortion. That is, she has given us a reason for thinking that abortion
is morally wrong. The conclusion of the argument is the first four words, “abortion is morally
wrong.” But whereas in the first example Sally was simply asserting that abortion is wrong (and
then trying to put down those who support it), in this example she is offering a reason for why
abortion is wrong.
We can (and should) be more precise about our definition of an argument. But before we can do
that, we need to introduce some further terminology that we will use in our definition. As I’ve
already noted, the conclusion of Sally’s argument is that abortion is morally wrong. But the
reason for thinking the conclusion is true is what we call the premise. So we have two parts of
an argument: the premise and the conclusion. Typically, a conclusion will be supported by two
or more premises. Both premises and conclusions are statements. A statement is a type of
sentence that can be true or false and corresponds to the grammatical category of a
“declarative sentence.” For example, the sentence,The Nile is a river in northeastern Africa is a
statement. Why? Because it makes sense to inquire whether it is true or false. (In this case, it
happens to be true.) But a sentence is still a statement even if it is false. For example, the
sentence, The Yangtze is a river in Japan is still a statement; it is just a false statement (the
Yangtze River is in China). In contrast, none of the following sentences are statements:
Please help yourself to more casserole
Don’t tell your mother about the surprise
Do you like Vietnamese pho?
The reason that none of these sentences are statements is that it doesn’t make sense to ask
whether those sentences are true or false (rather, they are requestsor commands, and
questions, respectively).
So, to reiterate: all arguments are composed of premises and conclusions, which are both types of
statements. The premises of the argument provide a reason for thinking that the conclusion is true. And
arguments typically involve more than one premise. A standard way of capturing the
