METHODS AND CONTENT OF TECHNICAL PHILSOPHY
(PART TWO)
B. CONTENT OF
PHILOSOPHY (CONT'): LOGIC
1. Introduction
It refers to the
study of correct reasoning. It deals with the structure and principles of sound
arguments. On our daily basis, individuals are engaged in various forms of
arguments, where premises/statements are made and conclusions drawn. In most
cases, wrong conclusions are arrived at involving wrong premises and undue
generalizations. Logic is essential because it stipulates how arguments should
be constructed and how fallacies (erroneous beliefs or myths) can be detected
and avoided. Within logic, two forms of reasoning can be distinguished:
deductive and inductive.
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2. Key concepts
a.
Mental Operations
1. Apprehension:
Deals with Conception (simple mental
grasp of an object-without further
operation),
2. Judgment
: Mental sentence or proposition(Affirm or deny)
3. Reasoning:
Argument( Drawing Inferences, dealing with premises and conclusion)
b. Reasoning: Mind's movement from one
or more propositions which act as evidence for a final proposition which calls
for proof.
c. Propositions: A proposition is any
statement with truth value i.e. it can be proved to be true or false. e. g.
Stones are cats. Propositions are never assessed in terms of validity. It's
either True or False.
d. Arguments: Is a set of Premises (evidential
propositions) and Conclusions(Claiming
propositions).
e. Quarrelling: Not same as arguing-
some of the statements in an quarrel are not propositions. Quarrelling is more
of a psychological activity than it is a Philosophical activity.
3. Some symbols used in
logic:
a. >
If......then...(symbol for Conditionality)
b. v Either.....or....(Symbol of disjunction)
c. ^ Both.....and.....(Symbol of Conjunctionality)
d. ≡
....If and only if...(Symbol of Bi-conditionality)
e. (
){ }[ ] Brackets are used to separate collective
Propositions
4.
Dimensions of Mordern logic
In modern philosophy, logic is expressed
in two main dimensions:
a.
Symbolic logic involving mathematical symbols –
application of symbols to explain phenomena e. g a + b = 4: b= 4 – a
b.
Analytic logic – prevalently used by analytic
philosophers who emphasize the logical analysis of language to arrive at
clear meanings of terms/concepts.
5. Types of arguments
i. Reductive Arguments ( Reductio ad
absurdum)
Reducing a
statement to its opposite or absurdity
P>-P
then -P
If it is not
raining then assume it's not raining
ii. Abductive Reasoning
Reasoning from
the best possible explanation
ABD1
Given evidence E
and candidate explanations H1,…, Hn of E,
infer the truth of that Hi which best explains E.
ABD2
Given evidence E
and candidate explanations H1,…, Hn of E,
infer the truth of that Hi which explains E
best, provided Hi is satisfactory/good enough qua
explanation.
ABD3
Given evidence E
and candidate explanations H1,…, Hn of E,
if Hi explains E better than any of the other
hypotheses, infer that Hi is closer to the truth than any of
the other hypotheses.
iii.
Dialectical Reasoning
Synthesis from a
Thesis and Anti thesis. No contradictions allowed
iv.
Deductive Reasoning
This involves
reasoning from general to particular instances. In this case, a conclusion is
inferred or deduced from general premises/statements/propositions.
Properties of a Deductive argument
a. Validity-( A deductive argument is
valid if the conclusion necessarily logically affirms the premises. It is
invalid if and only if it has all true premises and a False conclusion)
b. Soundness: (A sound Deductive
argument is one which has all actually/factually true premises and
true conclusion)
Examples
1. All
PGDE students are untrained teachers
John is a PGDE student
John is an untrained teacher
2. All
human beings are liable to make mistakes
Mike is a human being
Mike makes mistakes
3. All
human beings have sinned and fallen short of the glory of God
Mary is a human being
Mary has sinned and fallen short of the glory of God
4. All
numbers ending with 5 and 0 are divisible
by 5
1,964.5 Ends with 5
conclusion?...........
Further examples
Private schools
perform well in national exams
All Kikuyus are
thieves
All
Luos are proud
All
university students are immoral
Teachers
are hard working
All
Philosophers are idiots
All cats are dogs
The above
reasoning has been expressed in syllogism form: the first two statements
need to be stated before the third can follow logically. This type of reasoning
is prevalent in philosophy, religion and mathematics.
v. Inductive reasoning (Continue Editing)
It involves general laws/conclusions being
inferred from particular instances. It is the reverse of deductive reasoning.
In this type of reasoning, various instances of a given specimen are observed
over a period of time. The observation leads to general conclusions/laws being
established with some level of probability. This type of
reasoning is applicable with empirical sciences.
Example 1: P1. Most Kenyans are corrupt
P2. Otieno is a Kenyan
..............................................................................
Therefore
probably Otieno is corrupt
Example 2: P1.
There are 100 mangoes in the basket
P2. 70 of the mangoes
picked are rotten
...............................................................................
Probably all the
100 mangoes are rotten
Properties of Inductive reasoning
a Strength: An inductive argument is
said to be strong when it is when it is
such that when the premises are assumed
or granted to be true the its conclusion is most likely to be true.
b. Cogency: An argument is Cogent when it
is both strong and has actually true
premises
6. Selected Fallacies
7. Logic and Education
Students studying
science, arts or education should be familiar with the basic rules of logic so
as to enable one reason correctly and use language meaningfully throughout
their education Endeavour and in life
Thanks for the lecture
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