logic - module 3a inference (1)

8/3/2019 LOGIC - Module 3a Inference (1)

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³Teach a child WHAT to THINK and you

make him a slave of knowledge;

But, teach a child HOW to THINK and

you make knowledge his slave.´



Module 3a: REASONING ANDModule 3a: REASONING AND

INFERENCEINFERENCE

Pr epar ed by Mr . Roland Lor enzo M. RubenPr epar ed by Mr . Roland Lor enzo M. RubenPhilosophy section, SSDPhilosophy section, SSDDe La Salle Univer sityDe La Salle Univer sity -- Dasmar iñasDasmar iñas



OVERVIEW

1. Gener al Notion of Infer ence

2. Kinds of Infer encea. Immediate

b. Mediate



1. General Notion of Inference

The study of Logic is ver y for mative. Module 1 deals with ideas and terms which ar e the

basic elements of which judgments and pr opositions

ar e composed. Module 2 studies judgments and propositions, the

consistent arr angements of which constitute r easoning

or infer ence.



These studies ar e pr e-r equisites and pr epar ationto the under standing of r easoning or infer ence ±the 3r d division of Logic. At this stage, we enter logic proper.

Logic is the study of reasoning char acter izedby pr oducing r easons as evidence for a cer tainconclusion which we wish to establish.

1. General Notion of Inference



Reasoning is closely connected with infer ence.The r easons we pr ovide allows us to infer a

conclusion. R easoning is inference R easoning is inference. InferenceInference ± is a pr ocess in which f r om asequence of pr opositions we infer a conclusion,which is mar ked off as following f r om the for mer pr opositions.

The things we do with r easoning,

as a for m of communication, ar e:o Ar guing

o Explaining

o Making decisionso Pr edicting the futur e

o Explor ing issues

o Finding answer s

o Justifying actions



Suppose one wishes to establish the tr uth that ³ PedroSan Juan is a lawyer.´ Although ther e ar e many ways

of arr

iving at this tr uth, one way of p

r oviding evidencefor this conclusion is:

± (1) to asser t that ³All bar passers are lawyers.´ and,

± (2) ³Pedro San Juan is a bar passer .´

If both of these pr opositions ar e tr ue, then it follows that

³Pedro San Juan is a lawyer .´ It is impossible to asser t that ³Pedr o San Juan is a

lawyer ́ is false, if pr opositions (1) and (2) ar e tr ue:

Thus:1. All bar passers are lawyers.

2. Pedro San Juan is a bar passer. 3. Therefore, Pedro San Juan is a

lawyer.



2. KINDSOF INFERENCE

Ther e is a var iety of ways in which manr easons out.

Tr aditionally, these manner s of r easoningar e divided into 2 kinds:

1. Immediate Inference2. Mediate Inference



KINDSOF INFERENCE

Immediate InferenceImmediate Inference ± a pr ocess of r easoning which consists in passing dir ectlyf r om one pr oposition, without the aid of asecond pr oposition or a thir d ter m, called

medium, to a new pr oposition but not to anew tr uth.

± e.g. No vices are moral acts. Therefore, no moral acts are

vices.



KINDSOF INFERENCE

Mediate InferenceMediate Inference ± a pr ocess of r easoning in which f r om one pr oposition,with the aid of another pr oposition or a thir dter m, called medium, we infer not only a new

pr oposition but also a new tr uth. ± e.g. All bar passers are lawyers.

Peter St. John is a barpasser.

Therefore, Peter St. John isa lawyer.



summary

IMMEDIATE

The mind =

1. passes f r om one

pr oposition,

2. without a medium,

3. to a new pr oposition

but not to a new tr uth.

MEDIATE

The mind =

1. passes f r om two

pr opositions,2. with a medium,

3. to a new pr oposition

and at the same time

to a new tr uth.



Module 3a: REASONING AND INFERENCE

Next topic: Immediate Infer ence

logic - module 3a inference (1)

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