Junaid Ashraf

Logic is a study the methods and principles used to distinguish correct from incorrect reasoning.

Logic is also called Art of Arts and Science of Sciences.

It is a science of reasoning.

In logic we examine arguments of many varieties, in many spheres… argument in science and religion, ethics and law, politics and medicine, commerce and sports, and argument

arise in every day life.

LOGIC

Whatever the subject or content of an argument, the logician is interested in its form and its quality.

Does the argument do what it purpose to do?

If asserting the premises of some argument to be true does warrant asserting the conclusion also be true. Than the

reasoning is correct. Otherwise it is incorrect.

Propositions are either true or false, and in this they differ from questions, commands, and exclamations.

Only propositions can be either asserted or denied: questions may be asked and commands given and exclamations uttered, but none of them can be affirmed or denied, or judged to be

either true or false.

PROPOSITIONS

The difference between sentence and proposition is brought out by remarking that a sentence is always a part of a

language, whereas propositions are not peculiar to any of the languages in which they may be expressed.

It is raining (english)

Barsaat ho rai he (hindi)

Il pleut (french)

SENTENCE AND PROPOSITIONS

Simple proposition….A proposition making only one assertion.

Compound propositions…A proposition containing two or more simple propositions.

Disjunctive or Alternative Propositions….A type of propositions; if true at least one of the component proposition

must be true.

Hypothetical or conditional propositions …it is false only when the antecedents is true and the consequent is false.

KINDS OF PROPOSITIONS

An argument is not the mere collection of propositions, but has a structure. In describing this structure the term premise

and conclusion are usually employed

The conclusion of an argument is that proposition which is affirmed on the basis of the other propositions of the

argument

And these other propositions which are affirmed as providing grounds or reasons for accepting the conclusion are the

premises of that argument.

It should be noted that premise and conclusion are relative terms.

ARGUMENT

Inference …A process of linking propositions by affirming one propositions on the basis of one or more other propositions.

No proposition by itself, in isolation, is either a premiss or a conclusion.

It is a conclusion only when it occurs in an argument in which it is a claimed to follow from propositions assumed in that

argument. Like ‘employer’ and ‘employee’.

An argument always involves at least two proposition--- a conclusion plus one or more premisses.

The conclusion of an argument need not be stated either at its end or at its beginning. It can be, and often is, sandwiched

in between different premisses offered in its support.

ThereforeHence

SoAccordingly

In consequenceConsequentlyProves thatAs a result

For this reasonThus

For these reasons

SinceBecause

ForAs

Follows fromAs shown by

In as much asAs indicated by

The reason is that

Conclusion indicator Premise indicator

RECOGNIZING ARGUMENT

It follows thatI conclude that

Which shows thatWhich means thatWhich entails thatWhich implies that

Which allows us to infer thatWhich points to the conclusion

thatWe may infer

For the reason that

May be inferred from

May be derived from

May be deduced from

In view of the fact that

Conclusion indicator Premises indicator

It should be remarked that not every thing said in the course of an argument is either premise or conclusion of that argument. A passage containing an argument may also

contain other material, which is sometimes irrelevant but often supplies important background information that

enables the reader to understand.

Some passages may contain two or more arguments, either in succession, or intertwined.

In every argument one or more premises and a conclusion are asserted. But not every assertion of several propositions

constitute an argument

“if object of art are expressive, they are a language”

Such proposition is called a “conditional”.

No premiss is asserted, no inference is made, no conclusion is made to be true.

RECOGNIZING ARGUMENT

“Because objects of art are expressive, they are a language”.

Here we do have an argument.

A conditional statement may look like an argument, but it is not an argument; and the two should not be confused.

“synonyms are good servants but bad masters; therefore select them with care. (here there fore is a command rather than a proposition, and since a command is neither true nor

false. Premisses and conclusion must be asserted in an argument.

‘Since Henery graduated from medical school his probable income is very high’.

Since Henery graduated from medical school there have been many changes in medical techniques.

(in the second, the word “since” has temporal rather than logical significance.

Deductive----only deductive argument involves the claim that its premisses provide conclusive grounds for the truth of its

conclusion.

In the case of deductive arguments the technical terms “valid” and “ invalid” are used in place of “ correct” and

“incorrect”

DEDUCTION AND INDUCTION

Inductive-----inductive argument involves the claim that its premisses can not give coclusive grounds for its conclusion,

but only that they provide some grounds for it.

Inductive argument can be evaluated as better or worse.

In deduction we infer particular from general truths; while in inductionwe infer general from particular ……’