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HYPOTHETICAL PROPOSITION
Does not declare an unconditional affirmation or denial
Expresses a relation of dependence such as an opposition or a likeness between two clauses.
Kinds of Hypothetical Propositions
1. Conditional Proposition2. Disjunctive Proposition3. Conjunctive
Proposition
1. CONDITIONAL PROPOSITION
Expresses a condition or relation of dependence between two propositions
The expressed relation points out that one proposition necessarily follows from the other
Conditional Proposition
Examples:1. If animals can think, they are
rational.2. If the barometer falls, there will
be a storm.*** two parts are joined by if,
unless, when, where, suppose, in case
Conditional Proposition
“if-then” propositionsUsual structure: If A is B, then C is
D
Example:If dry weather continues, the harvest will be poor.
Two Component Propositions of a
Conditional Proposition1. Antecedent (Implicans)2. Consequent (Implicate)
Consequent (Implicate)
Expresses the statement that follows the acceptance of the condition i.e. the statement that depends upon the presence of the condition
The one that is conditioned.
Antecedent & Consequent
The antecedent precedes the consequent
Example:If a man is farsighted, he needs
eyeglasses. (Antecedent) (Consequent)
Antecedent & Consequent
A conditional proposition enunciates the dependence of the consequent upon the antecedent.
Dependence
The dependence is always logical i.e. we pass from the antecedent to the consequent in our thought or speech.
The dependence is real i.e. when the consequent depends on the antecedent in reality.
Dependence
Logical dependence: “If the ground is wet, it must have rained.”
Real dependence:“If it have rained, the ground would have been wet.”
2. DISJUNCTIVE PROPOSITION
One whose subject or predicate consists of parts which exclude each other.
“either-or” statementParts of a disjunction are called
disjuncts (alternants)
Disjunctive Proposition
Examples:1. A body is either in motion or at
rest.2. Man is the result of either of
creation or of evolution.3. Either the sun or the earth
moves in an orbit.
Proper Disjunction(perfect, complete,
strict) If and when the parts (disjuncts)
are mutually exclusive. Disjuncts can neither be true nor
false together at the same time.Examples:1. An individual is either honest or
dishonest.2. It is either raining or not raining.
Improper Disjunction (imperfect, incomplete)
One whose parts are not mutually exclusive.
One disjunct does not necessarily exclude the other.
Example:1. Jose is either sitting or writing.
Broad Disjunction
If and when at least one disjunct is true, but the other disjunct may also be true.
Example:1. Either my sister or I will go.
Strict or Broad Disjunction?Consider the content and context
within which occurs.A true, perfect, complete, strict &
proper disjunctive requires: 1. the enumeration of the possibilities must be complete. 2. there must be an exclusive
opposition between or among the enumerated possibilities.
3. CONJUNCTIVE PROPOSITION
One which denies that two contrary predicates together can be true of the same subject at the same time.
Denies the simultaneous possibility of two alternatives.
Conjunctive Proposition
Examples:1. You cannot stand and sit at the
same time.2. You cannot be in Quiapo and in
Makati at the same time.
Conjunctive Proposition
The truth of a conjunctive proposition depends solely upon a true exclusive opposition existing between their common parts.
The parts of a conjunctive are called conjuncts.
Conjunctive Proposition
Reducible to two connective hypothetical propositions or a combination of hypothetical and categorical propositions.
Reducing Conjunctive Proposition
Example:1.You cannot be in Quiapo and in Makati at the same time.
1.a. If you are in Quiapo, then you are not in Makati.
1.b. If you are in Makati, then you are not in Quiapo.
References
1. Celestine N. Bittle, The Science of Correct Thinking. Revised ed. (Milwaukee:The Bruce Publishing Co., 1950), 119-123.
2. Florentino T. Timbreza, Logic Made Simple for Filipinos. (Quezon City:Phoenix Publishing House inc., 1992), 50-53.
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