Dr. David R. Burgess
There are two criteria to consider when evaluating an argument:
There are formal methods to evaluate the first criterion. The possible worlds method is the most general method.
Identifying whether or not the rules for common deductive argument forms
(syllogisms, etc.) are followed would be another
method of deciding if the premises lead to the conclusion.
Many logical fallicies exist
and most beginning students find it helpful to stick to one deductive argument
form, like conditional syllogisms, in order to be certain that the premises
always lead to the conclusion.
- The premises must lead to the conclusion.
- The premises must be true.
The second criterion is often more difficult to determine since it requires
some sort of outside verification. Often the verification will be done by
making observations under controlled circumstances (performing experiments) or
drawing upon the experience of all human kind (using well-established theories).
In order for an argument to establish the truthfulness of a conclusion it must
be a sound argument, the premises must deductively lead to the conclusion and the premises
must be true.
- A deductive argument meets the first criterion, but the
process of determining if it is deductive still leaves the second criterion
undetermined. That is, the premises lead to the conclusion (without
question), but we don't know if the premises are true.
- A valid argument is a deductive argument. Different name,
- A sound argument must satisfy both criterion. The premises
must deductively lead to the conclusion and the premises must be true.
Brief summary of logical fallicies.