- The 4 main types of syllogisms
- 1- Class A. All S is P
- Example
- 2- Class E. All S are not P
- Example
- 3- Class I. Some S is P
- Example
- 4- Class O. Some S is not P
- Example
- References
There are different types of syllogisms: some are universal, others are particular; some admit a relationship between the subject and the predicate, and others deny it. Syllogisms are arguments of logical reasoning proposed by the philosopher Aristotle.
The objective of the syllogism is to establish the relationship between the subject and the predicate, using logical reasoning as a basis.
They are made up of three elements: two propositions and a conclusion. One of the propositions is the subject, which is also known as a minor premise.
The second proposition is the predicate, or major premise. For its part, the conclusion is the result of reasoning regarding the relationship between the subject and the predicate.
The effectiveness of the syllogism is based on the logic of comparative judgments. That is, it is through comparison that the relationship between the elements is established.
The premises can be universal or particular; this characteristic refers to the quantity that the syllogism covers.
In the universal premises the conclusion covers all the members of a group, while in the particular ones it only covers some members of a group.
There are syllogisms that establish a relationship between subject and predicate, these are affirmative relationships. On the other hand, the negatives are those that deny the relationship between the elements.
The affirmative and negative relations correspond to the quality elements of the syllogism.
The 4 main types of syllogisms
1- Class A. All S is P
This syllogism is the affirmative universal. In this kind of syllogism the judgment of quantity is universal and that of quality is affirmative.
In other words, class A is universal affirmative, and responds to the scheme of "every subject is the predicate."
Example
All men live on planet Earth.
2- Class E. All S are not P
The quantity judgment of this class is universal, so it integrates all members of the group. While the quality judgment is negative, implying that it does not apply to the subject's group.
Therefore the scheme that "no subject is the predicate" is applied, making a negative universal syllogism.
Example
No man can breathe underwater.
3- Class I. Some S is P
In this class it is inferred that the subject has the quality given by the predicate, for which the quality judgment is affirmative.
The quantity judgment is particular, because it is reduced to some members of the group. So in a particular affirmative syllogism. As such, it responds to the scheme "some subjects are predicated."
Example
Some men are astronauts.
4- Class O. Some S is not P
This class is also particular in its quantity judgment, because it refers to some of the members or elements of the group.
While his quality judgment is negative, denying the application of the predicate to the subject.
Then the result is a negative particular syllogism, the schema of which is "some subject is not the predicate."
Example
Many men have not gone to the moon.
References
- Syllogism (2017) collinsdictionary.com
- Syllogism definition (2017) literarydevices.net
- Categorical Syllogism (2011) philosophypages.com
- Syllogism (2017) webdianoia.com
- Syllogism (2017) philosophia.org
- What is a syllogism? (2017) vix.com