30 Questions
What is the main objective of equivalent propositions in the formulation of an argument?
To clarify the meaning of the original proposition
What is the process of eduction that involves changing the quality of the proposition and changing the predicate term to its contradictory or complement?
Ob-version
What is the role of the subject term in the process of ob-version?
To retain the quantity of the proposition
What is the result of changing the obvertend to its obverse?
A new proposition with the same meaning
What is the term used to describe the original proposition in the process of ob-version?
Obvertend
What is the purpose of the three rules in the process of ob-version?
To ensure the correct formation of the obverse
What is the main requirement of Rule 1 in conversion?
Change the subject and predicate of the convertend
What is the first step in applying the rules of obversion?
Retain the subject term and its quantity
What happens to the quality of the proposition in conversion according to Rule 2?
It is always retained
What is the result of obverting the proposition 'All senators are elected officials'?
No senators are non-elected officials
What is the implication of 'do not extend' in Rule 3?
Do not change the terms of the convertend
What is the type of conversion that allows a decrease in the quality of terms?
Partial conversion
Which of the following is a valid application of obversion?
A to E
What is the logical relationship between the obvertend and its obverse?
They are always logically equivalent
What is the result of violating Rule 3 in conversion?
A particular term becomes universal
What is the convertend in the example given?
Some women are politicians
What is the purpose of the third rule of obversion?
To substitute the predicate with a contradictory term
What is the result of obverting the proposition 'All Filipinos are Asians'?
No Filipinos are non-Asians
What is the difference between the convertend and converse of a proposition?
The convertend has a particular subject term and the converse has a universal predicate term
What is the process of combining conversion and obversion called?
Contraposition
What happens to the quality and quantity of the proposition during contraposition?
They are left unaltered
What is the result of applying Rule 1 of contraposition?
The subject term and predicate term are swapped
What is the purpose of Rule 2 of contraposition?
To substitute the new subject and predicate terms with their contradictory or complementary terms
What is the relationship between the contraponend and the contrapositive?
The contraponend is the original proposition and the contrapositive is the new proposition
What type of propositions is simple contraposition applicable for?
A to A and O to O propositions
What is the correct succession order for contraposition?
Contraponend, Obverse, Converse, Obverse
What type of proposition is 'All men are mortal beings' an example of?
A proposition
What is the contrapositive of the proposition 'All men are mortal beings'?
All immortal beings are non-men
What is the result of applying contraposition to 'Some birds are not flying animals'?
Some non-flying animals are not birds
What does the mnemonic 'ContrApositiOn' represent?
Legitimate in general for A and O propositions
Study Notes
Equivalent Propositions
- An equivalent proposition is a proposition with the same meaning or truth-value as the original proposition.
- It is the second type of immediate inference, also known as eduction or restating propositions.
The Three Equivalent Propositions (Eduction)
- Obversion
- Conversion
- Contraposition
Obversion
- A process of eduction consisting of two changes:
- Changing the quality of the proposition (leaving the quantity the same)
- Changing the predicate term to its contradictory or complement
- Three rules to observe:
- Retain the subject and the quantity of the proposition
- Change the quality of the proposition
- Substitute the predicate with a contradictory term
- Applicable to all four categorical propositions (A, E, I, O)
Conversion
- A process of eduction involving two changes:
- Switching the subject term and the predicate term (leaving the quality and quantity of the proposition unaltered)
- Three rules to observe:
- Retain the subject and the quantity of the proposition
- Retain the quality of the proposition
- Do not extend any term
- Two types of conversion:
- Absolute or simple conversion
- Partial conversion
Contraposition
- A process of eduction combining conversion and obversion
- Consists of two changes:
- Switching the subject term and the predicate term (leaving the quality and quantity of the proposition unaltered)
- Complementing both the new subject and predicate terms
- Three rules to observe:
- Interchange the subject and the predicate terms
- Substitute the new subject and predicate terms with their contradictory or complementary term
- Applicable only to "A to A" and "O to O" propositions under simple contraposition, and "E to O" propositions under partial contraposition. Not applicable to "I to I" propositions.
Learn about equivalent propositions, a fundamental concept in logical reasoning. Understand the importance of equivalent propositions in forming arguments and identify differences between main forms of education. Test your knowledge with this quiz!
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