1. Understanding Categorical Propositions
Categorical propositions are statements that assert relationships between categories or groups. There are three forms of categorical propositions:
- All: This indicates that every member of a category is included in another (e.g., All A are B).
- Some: This indicates that at least one member of a category is included in another (e.g., Some A are B).
- None: This indicates that no members of a category are included in another (e.g., No A are B).
2. Valid vs Invalid Deductions
Understanding valid and invalid deductions is crucial for logical reasoning. A valid deduction follows a logical structure where the conclusion necessarily follows from the premises. An invalid deduction, on the other hand, may appear logical but fails to connect the premises correctly.
Example of Valid Deduction:
1. All humans are mortal.
2. Socrates is a human.
Therefore, Socrates is mortal.
Example of Invalid Deduction:
1. Some cats are animals.
2. All dogs are animals.
Therefore, some dogs are cats. (This is invalid.)
3. Sample Practice Questions & Rationalizations
A) Some birds are cats.
B) All cats are birds.
C) All birds are cats.
D) None of the above.
Answer: D) None of the above. (The premises do not support any of the options.)
A) All apples are sweet.
B) Some apples are sweet.
C) No apples are sweet.
D) All sweet things are fruits.
Answer: B) Some apples are sweet. (This is a valid deduction based on the premises.)
A) Some cats are reptiles.
B) No cats are reptiles.
C) All reptiles are cats.
D) Some reptiles are mammals.
Answer: B) No cats are reptiles. (This follows directly from the premises.)
A) All students are thinkers.
B) Some students are thinkers.
C) No students are thinkers.
D) Some thinkers are students.
Answer: D) Some thinkers are students. (This conclusion is valid because it is a possibility based on the premises.)
4. Key Traps to Avoid & Test Day Tips
When practicing syllogisms, be cautious of common fallacies such as affirming the consequent or denying the antecedent. Always visualize the relationships using Venn diagrams, which can clarify connections between categories. On test day, ensure you read each question carefully, and use the process of elimination for multiple-choice options.
Ace the 2027 Philippine Civil Service Exam on Your First Try
Practice with 10,000+ updated questions, randomized mock exams, timed sub-tests, and instant explanations in the Civil Service Reviewer 2027 mobile app.
