This book has a fundamentally practical aim. It is concerned with the principles of intelligent thinking. When we understand these principles we shall be more reasonable in our thinking and better able to evaluate what we read and hear. We shall carry on our discussions, and even arguments, in a more civilized manner. We shall learn how to distinguish between a good argument and a bad man, or between a good man and a bad argument. We shall see how our emotions interfere with our thinking. And perhaps the reader will become a bit more impatient with the sensationalism, intemperance, vituperation, and caterwauling that is all too often substituted for an appeal to reason in public debates.
Thomas Jefferson, in a somewhat cynical mood, once said that newspapers ought to divide their news columns into four departments: Truths, Probabilities, Guesses, and Lies. Unfortunately, newspapers cannot always do this even though they may have the best intentions for they themselves do not always know which is which. A familiarity with the principles of semantics, logic, and scientific methods of thinking will help the reader to make these distinctions for himself. These principles will be examined as we go along.
Have you ever experienced a sense of being baffled and frustrated when someone accused you of being "Ulogical"? Do you know how to defend yourself against such a charge? The charge is unjustified as often as it is justified, so that even a slight acquaintance with logical principles will enable you to defend yourself against unjustified charges of this kind. The art of self-defense (not always the same thing as the art of making sense) gives one a sense of security, and this leads to more self-confidence. But, of course, it may have been the case that you were illogical. This might be because you committed a simple error you could easily have avoided if it had previously been pointed out to you. (Preferably in the quiet of your study rather than in the heat of controversy.) Logic, one of the essential elements in the activity of making sense, gives you a tool for checking your own thinking, as well as one for checking the thinking of others.