This is a PPT intended for Secondary School students. Some rules were not included for they may be very complex for the intended learners. Please COMMENT if this has become useful to you!

1. LOGICAL DEDUCTION

2. Deduction and Syllogism
 Deduction is a process of reasoning
where we begin with a general truth
to a particular conclusion.
 Syllogism is the set of arguments
that derives a conclusion from two
previous statements called
“premises”.

3. Quantity of Arguments
 Quantity
Universal- signaled by the qualifiers all
and no.
All humans are mortal beings.
No male is female.
Particular- signaled by the qualifiers
some, few, most of, not all, ect.
Some birds can fly.
Not all mammals live on land.

4. Quality of Arguments
 Quality
Affirmative- consenting to something.
All humans are mortal beings.
Some birds can fly.
Negative- negating or denying
something
No male is female.
Not all mammals live on land.

5. Premises and Terms of
Syllogisms

6. Major Premise
 The first argument that contains the Middle
Term and Major Term.
 Major Term is the predicate of the Major Premise
and the Conclusion.
 Example:
All mortal beings will die.
All human beings are mortal beings.
Therefore, all human beings will die.
Major Term
Major Premise

7. Minor Premise
 The second argument that contains the Minor
Term and the Middle Term.
 Minor Term is the subject of the Minor Premise
and the Conclusion.
 Example:
All mortal beings will die.
All human beings are mortal beings.
Therefore, all human beings will die.
Minor Premise
Minor Term

8. Middle Term
 The subject of the Major Premise and the
predicate of the Minor premise.
 Example:
All mortal beings will die.
All human beings are mortal beings.
Therefore, all human beings will die.
Middle Term
Middle Term

9. RULES FOR DERIVING
CONCLUSIONS FROM TWO GIVEN
PREMISES

10. Rule 1
 The conclusion must not
contain the Middle Term.
 Example:
No male is female.
John is male.

11. Rule 2
 No term can be distributed in the
conclusion unless it is distributed in
the premises.
 Example:
All cats have fur.
Some furs are orange.
Therefore, some fur are
cats???
some cats are

12. Rule 3
 The middle term should he distributed
at least once in the premises.
Otherwise, the conclusion cannot
follow.
 Example:
All cats have fur.
Some furs are orange.
Therefore, some fur are
cats???

13. Rule 4
 No conclusion follows if both the
premises are particular.
Example:
Some that can fly are birds.
Some ducks can fly.
Therefore, some ducks are
birds.

14. Rule 5
No conclusion follows if both
the premises are negative.
Example:
No mango is bitter.
No balsam apple is mango.
Therefore, no apple is
bitter???

15. Rule 6
 No conclusion follows if the major
premise is particular and the
minor premise is negative.
Example:
Some dogs are bulls.
No tigers are dogs.
No dogs are tigers.???

16. Rule 7
If one premise is negative,
the conclusion must be
negative.
Example:
All grasses are
trees.
No tree is shrub.

17. Rule 8
If one premise is particular,
the conclusion must be
particular.
Example:
Some boys are thieves.
All thieves are bandits.
Some boys are bandits.

18. Rule 9
If both the premises are
affirmative, the conclusion
must be affirmative.
Example:
All women are
mothers.
All sisters are women
All sisters are mothers.

19. Rule 10
If both the premises are
universal, the conclusion must
be universal.
Examples:
All mortal beings will die.
All human beings are mortal
beings.
Therefore, all human beings will
die.

20.  All humans will die.
 ___________________________
 Lito will die.

21.  ___________________________
 All whales are mammals
 All whales have lungs.

22.  All animals are living beings.
 Some flying objects are animals.
 ___________________________

23.  Angles <90° are Acute Angles.
 Angle ABC is 40°.
 ___________________________

24.  ___________________________
 Beef is a red meat
 Beef contains iron.

25.  All birds have feathers.
 ___________________________
 Roosters have feathers.