Jonathan Dolhenty, Ph.D. Logic and Critical Thinking.
TRUTH AND THINKING
Truth is the object of thinking.
Some truths are obvious; others are difficult to
Some judgments we make are simple; some
judgments are complicated.
Some arguments, whether made by us or others,
may be straightforward and easily understood;
other arguments may be complex and consist of a
series of smaller arguments, each needing to be
critically examined and evaluated.
CRITICAL THINKING AND LOGIC
Every object of knowledge has a branch of knowledge which studies it.
Planets, stars, and galaxies are studied by astronomy.
Chemistry studies the structure, composition, and properties of material
substances and the transformations they undergo.
The origin, evolution, and development of human society is the object studied by
Economics, biology, geography, and grammar all have objects of knowledge
which they investigate, describe, and try to explain.
WHAT ABOUT CRITICAL?
Critical thinking involves knowledge of the science of logic, including the skills of
logical analysis, correct reasoning, and understanding statistical methods.
Critical thinking, however, involves more than just an understanding of logical
A good critical thinker must also understand the sources of knowledge, the nature of
knowledge, and the nature of truth.
THE SCIENCE OF LOGIC
The object of knowledge involved in the science
of logic is "thinking," but it is "thinking"
approached in a special way.
Generally speaking, logic is that branch of
knowledge which reflects upon the nature of
But this may confuse logic with other branches of
knowledge which also have the nature of
"thinking" as a part of their specific object of
“THINKING” AND LOGIC
Logic doesn't just deal with "thinking" in general. Logic
deals with "correct thinking."
Training in logic should enable us to develop the skills
necessary to think correctly, that is, logically.
A very simple definition would be:
Logic is the subject which teaches you the rules for
correct and proper reasoning.
A more complete and "sophisticated" definition of logic, you
can define it this way:
Logic is the science of those principles, laws, and
methods, which the mind of man in its thinking must
follow for the accurate and secure attainment of truth.
A KIND OF LOGIC: NATURAL
“Natural Logic" or Common Sense
We all have an internal sense of what is
logical and what is not, which we generally
refer to as "common sense."
This "natural" logic we have learned from
the moment of birth, through our personal
experiences in the world and through our
acquisition of language.
A KIND OF LOGIC: SCIENTIFIC
Scientific logic is simply our natural
logic trained and developed to
expertness by means of well-
established knowledge of the principles,
laws, and methods which underlie the
various operations of the mind in the
pursuit of and attainment of truth.
LOGIC AS A SCIENCE
AND AN ART
Logic as a science:
The science part is the knowledge of the principles, laws, and methods of
Logic as an art:
Logic must be put into action or else the knowledge provided within the
science of logic is of little use.
We can speak of the "art" of logic, that is, the practical application of the
science of logic to our everyday affairs.
Logic as a science and an art
Logic is not intended merely to inform or instruct.
It is also a directive and aims at assisting us in the proper use of our power
In this sense, we can speak of logic as both a science and an art, a
practical art meant to be applied in our ordinary affairs.
Why Study Logic?
Aim: To develop a system of methods and
principles that we may use as criteria for
evaluating the arguments of others and as
guides in constructing arguments of our
Benefits: an increase in confidence that we
are making sense when we criticize the
arguments of others and when we advance
arguments of our own.
THREE OPERATIONS OF THE
OPERATIONS PRODUCT EXTERNAL
OF THE MIND SIGNS
Simple Concept / Idea Oral / written
Judgment Mental Oral / Written
Proposition Proposition or
Reasoning Mental Oral / written
agreement / argument
Simple Apprehension, Judgment,
Simple Apprehension: an operation of the mind
whereby we abstract from the non-essential elements
of a thing and recognize those essential elements
which make it to be precisely that particular thing.
Judgment: an operation of the mind which unites two
ideas by affirmation or separates by negation.
Reasoning / Mediate Inference: an operation of the
mind that involves a process whereby from certain
truths already known, we proceed to another which is
different from those that are given but necessarily
following from them.