LOGIC AND CRITICAL THINKING Jonathan Dolhenty, Ph.D. Logic and Critical Thinking. Available at

TRUTH AND THINKING Truth is the object of thinking. Some truths are obvious; others are difficult to acquire. 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. EXAMPLES: 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 sociology. 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 procedures. 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 "thinking" itself. 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 investigation.

“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 LOGIC “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 LOGIC 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 itself. 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 of reasoning. 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 own. 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 MIND OPERATIONS OF THE MIND PRODUCTEXTERNAL SIGNS Simple Apprehension Concept / IdeaOral / written terms JudgmentMental Proposition Oral / Written Proposition or statement ReasoningMental agreement / disagreement Oral / written argument

Simple Apprehension, Judgment, Reason 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.