DAY8 More Categorical Syllogisms.docx - DAY8 More...

DAY8 More Categorical Syllogisms
All that we have studied so far this semester is foundational to understanding what logic is, what
it does, and how it can help us seek the truth through reasoning. As you know, we are in the
middle of learning a logic system called Categorical Logic, developed by Aristotle and further
elaborated in the Middle Ages and nineteenth century. There is much more to learn about
Categorical Logic this semester, but before we add more information to learn we need to ensure
that we have mastered the foundational information.
This lecture is intended to heighten our skills in using Categorical Logic. So far, most of the
categorical syllogisms we have evaluated have been in standard form. Standard form? This
means, among other things, that the argument consists of standard form A, E, I, or O statements,
and that they are presented with the premises above the conclusion, and specifically with the
major premise on top. As we know from experience, most people do not write and speak in
standard form. So, it is important for us to keep improving our skill of analyzing written
arguments into standard form. Why? Once an argument is placed in standard form, we can
evaluate it easily (by using three-circle Venn diagrams and the four syllogistic rules).
A valuable step in analyzing an argument into standard form is to identify indicator words, as we
know. Take a moment and reacquaint yourself with the two lists below. We saw these two lists at
the beginning of the semester. These lists present the most commonly used indicator words and
phrases.
Premise indicators :
Because
Since
As
For
Given that
Inasmuch as
Due to
As a result of
Seeing that
Owing to the fact that
Conclusion indicators :
Therefore
Thus
Hence
So
It follows that
We may conclude that
Ergo
Consequently
Accordingly

We may infer that
For this reason
It is necessarily the case that
Recall that not every argument in speech and writing has indicator words; and remember that
some arguments will only have premise indicators but not conclusion indicators, or vice versa;
and some writers and speakers will misuse indicator words. Whenever we encounter indicator
words used well, we are wise to let them help us separate premises from conclusion. The
homework assignment below gives multiple opportunities to refine our skill of letting indicator
words help us analyze arguments into standard form . Once an argument is analyzed into standard
form, we can easily evaluate the argument for validity