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Ask, "How good is the evidence?" Evidence may be based on
scientific experimentation, after-the-fact correlations (smoking
and cancer), case studies (the effects of divorce on children), or
an appeal to the most convincing situation (torture is justified
to save hundreds of lives). Doubt any claim that something has
been "proven;" scientists say, "The evidence to date
suggests...." Search for and collect evidence for a different
conclusion. Evaluate the data, the supporting facts, and the
reasoning; ask yourself repeatedly how strongly the conclusion
is supported by the evidence.
When reasoning deductively, you start with a statement
about "all," "every" or "only," and the conclusion logically
follows: (1) Everyone in my group of friends likes rock music.
(2) Bill is in my group. (3) Therefore, Bill likes rock. The real
question is if (1), the generalization, is accurate.
When using another form of reasoning called inductive, you
start with some specific observations and draw generalizations:
(1) I noticed that many students in my school like rock music.
(2) Therefore, "most" students like rock music. The question
here is: Have you made enough accurate observations to
warrant making the "inductive leap" to most students in your
school? to students in the state? to students everywhere in the
world? Statisticians use careful sampling techniques and
statistics to make accurate predictions, such as what people will
buy or how they will vote.
Look for the assumptions being made. If someone says,
"Abortion is murder," one has to question the term murder. The
dictionary says murder is the killing of one human being by
another. When is a fetus a human being? When its heart beats
(15 days)? When it has brain waves (4th month)? When it has
a 50-50 chance of surviving on its own without massive medical
assistance? When he/she is born at full-term? These are
improvable personal opinions, individual beliefs, but they are
critical to the idea of murder. Unfortunately, emotional issues,
like "Abortion is murder," get infused with dogmatic religious
beliefs which the believers would like to force on others.
If someone says, "Students are either serious or party
animals," the assumption is being made that students can not
be both serious and party-lovers and that students can not be
disinterested in both studies and parties.
In most arguments, there are many assumptions about
both values and facts. Many are subtle, e.g. that hiring the
"best person" is better than affirmative action, that personal
gain is of more value than serving others, that expressing
anger reduces future anger, and so on. Uncover the
assumptions being made and decide if you agree with them.
