Arguments

Arguments

EXTENDED ARGUMENTS

So far we have been dealing with categorical arguments but there are other forms of arguments which are not categorical. Because, they have less or more propositions than the standard form categorical arguments. They include;

  • Enthymeme
  • Sorites
  • The hypothetical syllogism
  • The disjunctive syllogism
  • Dilemma
  1. ENTHYMEME

An enthymeme is a valid syllogism with one of the premises or conclusion suppressed.

There are basically three kinds of enthymeme depending on the part of the argument suppressed

  1. The first order enthymeme: this is one in which the major premise is omitted such that the only the minor premise and conclusion are stated
  2. The second order enthymeme: this is one in which the minor premise is omitted such that only the major premise and the conclusion are stated.
  • The third order enthymeme: this is one in which the conclusion is suppressed in such a way that only the major premise and the minor premise are visible.

Schematically, the three orders of enthymeme can be summarized as follows

enthymeme major premise Minor premise Conclusion
First order …………………. SM SP
Second order MP ……………… SP
Third order MP SM …………………

 

 

S=subject term

P=predicate term

M=middle term

Expressing syllogism into their enthymematic order

To express a syllogism as an enthymeme of the first order, write the conclusion first then link it to the minor premise using “since or because” there by omitting the major premise. For the second order, do the same but just that you instead omit the minor premise.

To write the enthymeme of the third order, write the major premise first and then link it the minor premise using “and” there by omitting the conclusion.

EXAMPLE

All carnivores are animals

All lions are carnivores

Therefore all lions are animals

First order: all lions are animals since all lions are carnivores

Second order: all lions are animals because all carnivores are animas

Third order: all carnivores are animals and all lions are carnivores

 

  1. HYPOTHETICAL SYLLOGISM

This is one in which all the propositions are hypothetical or the major premise is hypothetical. There are two forms of hypothetical syllogism; the pure and the mixed hypothetical syllogism

  1. Pure hypothetical syllogism

This is a hypothetical syllogism whose propositions or premises are all hypothetical

Example

If Shekinah works hard, she would pass her exam.

If she passes her exam, she would go to Europe.

Therefore if Shekinah works hard, she would go to Europe.

Valid form of hypothetical syllogism

For a hypothetical syllogism to be valid, the component parts of the premises should be related to the component parts of the conclusion.

  • e. The antecedent of the major premise and the antecedent of the conclusion should be the same
  • The consequence of the minor and that of the conclusion should be the same
  • The consequence of the major premise should be the same as the antecedent of the major.

EXAMPLE: see example above

  1. The mixed hypothetical syllogism

This is a syllogism whose major premise is hypothetical while the minor premise and conclusion are categorical.

There are two forms of hypothetical syllogism: namely the modus ponens and the modus tollens

  1. Modus ponens

The word “ponens” comes from the Latin word “ponere” which means “affirm”. So the modus ponens means I affirm. It is therefore a syllogism whose minor premise affirms the antecedent of the major and the conclusion affirms the consequence of the major

Form of the valid modus ponens

If A is B then A is C                    OR              if A is B then C is D

A is B                                                                      A is B

Therefore A is C                                                  then C is D

EXAMPLE

If man is a free being then he is master of his destiny

Man is a free being

Therefore he is master of his own destiny

  1. Modus tollens

In an invalid modus tollens minor premise denies the antecedent of the hypothetical major premise while the conclusion denies the consequence of the hypothetical major premise.

FORM

If A is B, then C is D              OR                         if A is B then A is C

A is not B                                                              A is not B

Therefore C is not D                                           therefore A is not C

 EXAMPLE

If Denuel  is an engineer, then he can manufacture computers

Denuel is not an engineer

Therefore he cannot manufacture computers

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