FORMAL AND INFORMAL LOGIC
"
We do affirm that if truth is to be sought in every division of philosophy, we
must, before all else, possess trustworthy principles and methods for
discernment of truth. Now the logical branch is that which includes the
criteria and proofs; so it is with that we ought to make our beginnings."
(SEXTUS EMPERICUS)
INTRODUCTION
Logic generally, both formal and
informal, is primarily concerned with the normative distinction between good
and bad reasoning, interpret good reasoning as minimally deductively valid
inference.
The aim of this paper is to examine
the similarities between Informal and Formal Logic. To accomplished the goal of
this paper we shall look at the definition of Logic by different Logician. This
shall be followed by the definitions of Informal Logic and that of Formal
Logic. Afterward we shall compare and contrast informal and formal logic, in a
tabular form. More so, I shall elucidate the three laws of thought of Logic.
Then we shall conclude.
WHAT IS LOGIC
Logic has been define in different
ways. According to Irving M. Copi, Logic is the study of the methods and
principles used to distinguish good (correct) from bad (incorrect) reasoning.[1] Logic is sometimes define
as the science of reasoning, Logic is that branch of philosophy that deals with
the study of the basic principles,
techniques or methods for evaluating arguments.[2] Evaluation here involves
making a distinction between good and bad, valid and invalid, deductive and
inductive as well as sound and unsound arguments. It is the study of the
methods and principles used to distinguish correct reasoning from incorrect
reasoning.
Logic has three Laws of Thought
which are: The Law of Identity, The Law of Contradiction and The Law of
Excluded Middle. The Law of Identity states that if any statement is true, then
it is true. The Law of Contradiction says that no statement can both be true
and false at the same time. Finally, the Law of Excluded Middle, states that
any statement is either true or false.
The Value of Logic is that, its
points out the possible ways in which, starting from a true premises we may
draw a false conclusion (bad reasoning or invalid argument). It enables us to
guard the points at which a fallacy is in danger of slipping in, or to lay our
fingers upon the place where it has slipped in. Logic help to clears up the
fogs which hide from our own ignorance, and makes us believe that we understand
a subject when we do not.
INFORMAL LOGIC
Informal logic is a branch of logic
whose task is to develop non-formal standards, criteria, procedures for the
analysis, interpretation, evaluation, criticism and construction of
argumentation in everyday discourse. [3]Informal Logic is concerned
mainly with our everyday activities of making and evaluating claims, as well as
detecting errors in reasoning.[4] Informal logic is also an attempt to develop a logic that can assess and
analyze the arguments that occur in natural language discourse. Informal logic combines logic's
traditional emphasis on inference with the study of a broad range of topics
relevant to informal reasoning. It include, competing definitions of
“argument”, argument identification, burden of proof, the empirical study of
argument, diagramming, cognitive bias, the history of argument analysis,
methods of argumentative investigation, the role of emotion in argument or
informal fallacies, exercise in reasoning and the implicit rules that
characterize argumentative exchange in different social contexts. Informal
logic is commonly regarded as an alternative to formal or mathematical logic.
Informal logic as a field, has to do with the uses of argumentation in a
context of dialogue, an essentially pragmatic undertaking. Also known as non-formal logic or critical thinking or inductive
logic because
Reasoning based on informal, inductive logic moves from statements of evidence
(the premises) to a conclusion that extrapolates from, amplifies, or
generalizes the evidence.
Example: Fast food is high in fat, salt and
calories,
Fast food has little
nutritional value,
Therefore, if I eat fast
food, I will be unhealthy.
FORMAL LOGIC
Formal Logic deals with the logical
or formal structures of statements and arguments.[5] Formal logic has to do with the forms of argument (syntax) and truth values (semantics). It is also
seen as the branch of logic that examines patterns of reasoning to
determine which ones necessarily result in valid, or formally correct.
It can also be called deductive logic because
the form of thinking allows one to deduce its conclusion from its premises. It
is a Classical or traditional system of determining the validity or invalidity of a conclusion (inference) deduced from two or more statements (premises).
Example: If it rains, I will get wet
It has rain
Therefore I am wet.
There are three
things that makes Logic Formal which are:
·
In the sense that it provides constitutive
norms for thought as such.
·
In the sense that it is indifferent to the
particular identities of objects.
·
In the sense that it abstracts entirely
from the semantic content of thought.
|
INFORMAL
LOGIC
|
FORMAL
LOGIC
|
|
Informal
logic would be better named NON- FORMAL logic. It contends specific terms, it
can suffer from structural invalidity. But the fallacies which are unique to
informal logic relate to the unsoundness of the premises.
|
Formal
logic is entirely structural and tautological (deductive). All fallacies in
formal logic relate to invalidity. Intra-argument structural errors and
inconsistencies.
|
|
Informal
fallacies occur when the reasoning or rationale behind the specific content
of a premises is illogical. i.e. they support content of the argument relies
on the rhetoric.[6]
|
Formal
fallacies are errors in logic that are due entirely to the structure of the
argument, without concern to the content of the premises. They can be
referred to as non sequitors.[7]
|
|
Informal
arguments are much more common, they tend to be complex and contained
unstated assumptions.
|
Formal
argument tend to be simple, straight forward, and extreme.
|
|
The
both operate on the level of deductivism, because, they have common concern
with exact distinction between good and bad reasoning, promotion of good
reasoning.
|
CONCLUSION
From
the foregoing, we have seen that Logic for Irving M. Copi is the study of the
methods and principles used to distinguish good (correct) from bad (incorrect)
reasoning. Afterward we examine Logic's Three laws of thought which are The Law
of Identity that states that if any statement is true, then it is true. The Law
of Contradiction says that no statement can both be true and false at the same
time. Finally, the Law of Excluded Middle, states that any statement is either true
or false. More so, we consider the definitions of Informal and Formal Logic.
Finally we compared and contrasted informal and formal logic in a tabular form.
[5] Francis
Offor, Ph.D, Essentials Of Logic, Revised
Edition
[6] Copi. I. M. Cohen, C., (2001), Introduction to Logic, 11 edition
[7] Copi. I. M. Cohen, C., (2001), Introduction to Logic, 11 edition
Comments
Post a Comment