An inductive argument is intended to provide only probable
support for its conclusion, being considered strong if it succeeds in
providing such support and weak if it does not.
Inductive arguments come in several forms, including
enumerative, analogical, and causal. In enumerative induction, we argue
from premises about some members of a group to a generalization about the
entire group. The entire group is called the target group; the observed
members of the group, the sample; and the group characteristics we’re
interested in, the relevant property.
An enumerative induction can fail to be strong by having a
sample that’s too small or not representative. When we draw a conclusion
about a target group based on an inadequate sample size, we’re said to
commit the error of hasty generalization.
Opinion polls are enumerative inductive arguments, or the basis
of enumerative inductive arguments, and must be judged by the same general
criteria used to judge any other enumerative induction.
In analogical induction, or argument by analogy, we reason that
since two or more things are similar in several respects, they must be
similar in some further respect. We evaluate arguments by analogy
according to several criteria: (1) the number of relevant similarities
between things being compared, (2) the number of relevant dissimilarities,
(3) the number of instances (or cases) of similarities or dissimilarities,
and (4) the diversity among the cases.
A causal argument is an inductive argument whose conclusion
contains a causal claim. There are several inductive patterns of reasoning
used to assess causal connections. These include the Method of Agreement,
the Method of Difference, the Method of Agreement and Difference, and the
Method of Concomitant Variation.
Errors in cause-and-effect reasoning are common. They include
misidentifying relevant factors in a causal process, overlooking relevant
factors, confusing cause with coincidence, confusing cause with temporal
order, and mixing up cause and effect.
Crucial to an understanding of cause-and-effect relationships
are the notions of necessary and sufficient conditions. A necessary
condition for the occurrence of an event is one without which the event cannot
occur. A sufficient condition for the occurrence of an event is one that
guarantees that the event occurs.