Is
the text an argument?
An argument here doesn't mean a dispute or controversy.
It means an attempt to provide a reason for believing something
by citing something else. It is an attempt to show that something
is true, or probably true, by appealing to something else, some
reason or evidence, which indicates that it is true.
The following text includes an
argument:
New evidence shows that the AIDS
virus may not be as lethal as it has been thought to be and that
some people may be able to develop a defense against it. The
evidence involves an appreciable number of people who have been
HIV positive for many years (some of them for twelve years or
more). Lab tests show that the virus is present in their blood.
But they have not developed any symptoms of AIDS. They continue
to be in good health and show no signs of developing the disease.
Some researchers estimate that as many as 5% of those infected
by the virus may be in this category and that they will never
develop the disease.
In
this text a claim is made about how lethal the AIDS virus is.
It may not be 100% lethal. Some people may be able to resist
it, perhaps because of a natural immunity. And some evidence
is cited to show that this claim is true. That evidence is the
(alleged) fact that some people have had the AIDS virus in their
system for many years and show no signs at all of developing
the disease. It is plausible to think that the person who wrote
that text intended to cite that fact as a reason for believing
the claim about the lethality of the AIDS virus.
Premises and Conclusions
In
an argument some claims are put forward in support of
others. The claim that is being supported is the conclusion.
The claims which are alleged to support the conclusion are the
premises. There may be more than one conclusion in an
argument, and often, there is more than one premise. In the argument
above about AIDS, there is a closely related set of conclusions.
New evidence shows that the
AIDS virus may not be as lethal as it has been thought to be
and that some people may be able to develop a defense against
it.
In
support of these conclusions, the author cites the (alleged)
fact that some people have been infected with the virus for a
long time without showing any signs of the disease itself. This
latter assertion is the premise in this argument.
How
do you identify premises and conclusions? Reliable clues are
provided by certain key words, which are often used to identify
premises and conclusions. The following words and phrases are
quite often used to introduce conclusions:
So...
This shows that...
Therefore...
We can infer that...
Hence...
Consequently...
It follows that...
This indicates that...
For that reason, we may say...
These are phrases that introduce
the premises of an argument:
The reason is that...
Because...
Since...
Evidence...
On the basis of...
It follows from...
In view of...
We may infer from...
When
you are able to identify premises and conclusions, you may easily
analyze how strongly the premises back up the conclusion. In
many of the Critical Reasoning questions, there will be a gap
between the premises and the conclusion--the assumptions. Your
objective is to find the gaps (the assumptions) and use that
knowledge to find the solution. For example, in the AIDS argument
above, one of the unstated assumptions is that the evidence about
AIDS is accurate.
