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Kinds of Propositions

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Sam Dayrit

on 19 September 2014

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Transcript of Kinds of Propositions

Kinds of Propositions
In logic there are many kinds of propositions –

categorical or attributed,
hypothetical,
existential,
non-existential,
simple,
compound, etc.

We shall treat of the categorical proposition first in the following pages.
Categorical Proposition
In logic, a categorical proposition, or categorical statement, is a proposition that asserts or denies that all or some of the members of one category (the subject term) are included in another (the predicate term).
Hypothetical Proposition
A hypothetical proposition is one whose predicate does not assert of the subject in an absolute manner.


There are three kinds of hypothetical propositions:
1. Conditional Proposition
2. Disjunctive Proposition
3. Conjunctive Proposition

An existential proposition (or statement) is one affirming the existence of some thing or kind of things—for instance, ‘The yeti exists’ or ‘Unicorns exist’.


Problems arise over the interpretation of negative existential statements, especially singular ones like ‘The yeti does not exist’, because the singular term which functions as the grammatical subject of such a statement seems to make reference to an object which, if the statement is true, does not exist.
Existential Propositions
Expresses a condition or relation of dependence between two propositions. Expressed relation points out that one proposition necessarily follows from the other because of a definite condition. Note that a conditional proposition is one in which two parts are joined by if, unless, when, where, suppose, in case. Sometimes called an if-then proposition
 Conditional Proposition 
Examples: If a man is farsighted, he needs eyeglasses.
If dry weather continues, the harvest will be poor.
One whose subject or predicate consists of parts which exclude each other. Sometimes called an either or statement due to its construction. Parts of disjunction are called disjuncts (alternants)
 Disjunctive Proposition 
Examples: A body is either in motion or at rest.
Either Pedro or Juan is dishonest.
One which denies that two contrary predicates together can be true of the same subject at the same time. The truth of a conjuctive hypothetical proposition depends solely upon a true exclusive opposition existing between their component parts. Parts of conjuctive are called conjucts
 Conjuctive Proposition 
Examples: You cannot stand and sit at the same time.
You cannot be in Quiapo and in Makati at the same time.
Basic Elements of the Categorical Proposition
The subject is the one spoken of, the one about whom or of which something is affirmed or denied. In most cases the grammatical subject corresponds with the logical subject.


In some instances, however, it does not. In “We ought to give the Boy Scout Award to Arturo,” the grammatical subject is “we,” but in most cases, the logical subject would be “the one to whom we should give the Boy Scout Award.”
*The predicate is what is affirmed or denied of the subject.




*The copula links the subject with the predicate. It is the verb to be:

is, am, are (affirmative) and is, am, are not (negative).
For purposes of logic, tenses are irrelevant.


The copula “is” should be taken in a tenseless sense; its past and future forms are usually considered part of the predicate.

Thus. “Magellan was the discoverer of the Philippines” may be read as Magellan is the Span lard who discovered the Philippines.” Again: “Red China will be the country to watch.”
In this connection it is important to note that number, in the grammatical sense, is irrelevant also to logic.


“A horse is an animal” is equivalent to “All horses are animals.” No distinction what so ever is made between “horse” and “horses” and between “animal” and “animals.”
Quality of the Proposition
The copula is the qualifier of the propositions. Because of it, the proposition is either affirmative or negative.


The following are considered affirmative but equivalently negative statements:


1. He who is not a college graduate is ineligible.
2. Some animals are non-mammals.

Quantity or Extension of the Proposition
The quantity of the proposition is equivalent to the quantity of its subject. It is singular if the subject stands for a single definite individual or group; it is particular if the subject designates an indefinite part of its total extension; and it is universal if the subject can apply to every portion signified by the term.


The quantifiers - every, each, all, some, several, many, etc. – play a significant role.
Examples




1.
Singular
: Shakespeare is England’s greatest dramatist.

2.
Particular
: Some prima ballerinas are Margot Fonteyn and Natalia Makarova.

3.
Universal
: Love is a many-splendored thing.

Quantity of the Predicate
Aristotelian logic consigns matter to the subject and form to the predicate.


In “Mars is a planet,” the predicate “planet” supplies the form that is received into the subject “Mars”. Initially attention is focused on the predicate as involving comprehension. Not extension or quality; only later does it dawn on the mind that the quantity of the subject is drawn into the quantity of the predicate.

This does not mean to say that the quantity of the predicate is equivalent to the quantity of the subject.
Determining the quantity of the predicate is simple. There are only three points to keep in mind. These are:




1. Find out first if the predicate in singular. It is singular if it refers to a single definite individual or group (exactly the same signs of singularity as for the subject.) The proposition may be either affirmative or negative.

The categorical or attributive proposition has a subject-predicate relationship: its subject is affirmed or denied by the predicate.


Its basic elements, therefore, are:

*The subject
*The predicate
*And the copula

*In the statement, “The story he told you is apocryphal,”


the subject is
story


*The predicate is apocryphal (which means fictitious)


The copula is
is
.

Thank You! :)
By:

Christine Joyce Pamandanan
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