The document discusses syllogistic figures and principles of categorical syllogism. It explains: 1) Four syllogistic figures defined by the location of the middle term in the premises. 2) Five principles of categorical syllogism including reciprocal identity, reciprocal non-identity, dictum de omni, dictum de nullo, and contradiction. 3) Basic rules of categorical syllogism requiring three terms, limitations on negatives, and conclusions matching premises. 4) For a syllogism to be valid it must be correct in form and have true content.

1. SYLLOGISTIC FIGURES
Figure 1 (Sub – Pre)
M–T A dog is an animal.
t–M But a puppy is a dog.
t–T :. A puppy is an animal.
Take note of the location of the M

2.  Figure 2 (Pre – Pre)
T–M Every man is a thinker.
t–M But a fish is not a thinker.
t–T :. A fish is not a man.
Note: focus on the location of the M

3.  Figure 3 (Sub – Sub)
M–T Some vegetables are cabbages.
M–t But all vegetables are plants.
t –T :. Some plants are cabbages.
Note: Where’s the M?

4.  Figure 4 (Pre – Sub)
T – M Some Filipinos are Igorots.
M – t But all Igorots are God-created.
t – T :. Some God-created beings are
Filipinos.
Again note the location of M

5. Principles of Categorical Syllogism
1. Principle of Reciprocal Identity
Briefly expressed:
A is B God is divine.
But C is B. But Jesus is divine.
:. A is C. :. God is Jesus.

6. 2. The Principle of Reciprocal Non –
Identity
Briefly expressed:
A is B. All plants are living
things.
But c is not A. But stones are not
plants.
:. C is not B. :. Stones are not
living
things.

7. 3. The Principle of Dictum de Omni
What is affirmed universally of a
given term is affirmed of everything
found within the extension of said
term.
For instance what is affirmed of the
term “creature” can be affirmed of
man, animals and plants which are
extension ideas of the idea creature.
If creatures are mortal then man,
animals and plants are _______.

8.  4. The Principle of Dictum de Nullo
 Opposite of dictum de omni. What
is negated universally of a given term
is likewise negated of every term
found within the extension of the said
term.
 If a plant is not a stone all extension
ideas of the idea plant is not a stone.

9. 5. The Principle of Contradiction
If a THING IS, it cannot be IS NOT
at the same time. If this is a table,
then it cannot be that this is not a table
at the same time.

10. Basic Rules of Categorical
Syllogism
1. There must be only three (3)
univocal terms.
2. There can be no two (2) negative
premises.
3. On quality, if the 2 premises are
affirmative the conclusion is
affirmative.
4. The conclusion is negative if one of
the premises is negative.
5. The conclusion must be particular if
one of the premises is particular.

11. 6. In terms of quantity, there must be
no 2 particular premises. One
premise must be at least universal.

12. VALIDITY and TRUTH IN SYLLOGISM
Two Conditions:
1. Correct in form
2. True in content.
◦ A syllogism may be correct in form but
false in content. Or may be incorrect in
form but true in content. To be a valid
categorical syllogism the form must be
correct and the content must be true.