Almost 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 sociology. Economics, biology, geography, and grammar all have objects of knowledge which they investigate, describe, and try to explain.
Critical thinking involves a 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. But first, what is 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. We need a more detailed and accurate definition to eliminate any confusion.
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. For those of you who want 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. Take your choice.
Natural Logic and Scientific Logic
We need to be aware of a distinction between what some call "natural logic" or common sense and "scientific" logic. 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. Scientific logic, on the other hand, 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.
We have referred to the "science" of logic but logic is really more than just a science. The science part is the knowledge of the principles, laws, and methods of logic itself. This is important, to be sure. But logic must be put into action or else the knowledge provided within the science of logic is of little use. We can, therefore, also speak of the "art" of logic, that is, the practical application of the science of logic to our everyday affairs. Logic is not intended merely to inform or instruct. It is also 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.
Logic and Psychology
We want to be sure that we don't confuse the science of logic with the science of psychology. Psychology also studies "thinking," but it is a separate, autonomous discipline of its own. And logic is not a...