The study of the common _fallacies_, such as “Begging the Question,” “Reasoning in a Circle,” etc., is particularly important to the student, for when one realizes that such fallacies exist, and is able to detect and recognize them, he will avoid their use in framing his own arguments, and will be able to expose them when they appear in the arguments of others.
The fallacy of “Begging the Question” consists in assuming as a proven fact something that has not been proven, or is not accepted as proven by the other party to the argument. It is a common trick in debate. The fact assumed may be either the particular point to be proved, or the premise necessary to prove it. Hyslop gives the following illustration of this fallacy: “_Good institutions should be united_; Church and State are good institutions; therefore, Church and State should be united.” The above syllogism seems reasonable at first thought, but analysis will show that the major premise “Good institutions should be united” is a mere assumption without proof. Destroy this premise and the whole reasoning fails.
Another form of fallacy, quite common, is that called “Reasoning in a Circle,” which consists in assuming as proof of a proposition the proposition itself, as for instance, “This man is a rascal, _because he is a rogue_; he is a rogue, _because he is a rascal_.” “We see through glass, _because it is transparent_.” “The child is dumb, _because it has lost the power of speech_.” “He is untruthful, _because he is a liar_.” “The weather is warm, _because it is summer_; it is summer, _because the weather is warm_.”
These and other fallacies may be detected by a knowledge of Logic, and the perception and detection of them strengthens one in his faculty of Deductive Reasoning. The study of the Laws of the Syllogism, in Logic, will give to one a certain habitual sense of stating the terms of his argument according to these laws, which when acquired will be a long step in the direction of logical thinking, and the culture of the faculties of deductive reasoning.
In concluding this chapter, we wish to call your attention to a fact often overlooked by the majority of people. Halleck well expresses it as follows: “Belief is a mental state which might as well be classed under _emotion_ as under thinking, for it combines both elements. Belief is a part inference from the known to the unknown, and part feeling and emotion.” Others have gone so far as to say that the majority of people employ their intellects merely to _prove_ to themselves and others that which they _feel to be true_, or _wish to be true_, rather than to ascertain what is _actually true_ by logical methods. Others have said that “men do not require _arguments_ to convince them; they want only _excuses_ to justify them in their feelings, desires or actions.” Cynical though this may seem, there is sufficient truth in it to warn one to guard against the tendency.
Jevons says, regarding the question of the culture of logical processes of thought: “Monsieur Jourdain, an amusing person in one of Moliere’s plays, expressed much surprise on learning that he had been talking prose for more than forty years without knowing it. Ninety-nine people out of a hundred might be equally surprised on hearing that they had long been converting propositions, syllogizing, falling into paralogisms, framing hypotheses and making classifications with genera and species. If asked if they were logicians, they would probably answer, No. They would be partly right; for I believe that a large number even of educated persons have no clear idea of what logic is. Yet, in a certain way, every one must have been a logician since he began to speak. It may be asked:–If we cannot help being logicians, why do we need logic books at all? The answer is that there are logicians, and _logicians_. All persons are logicians in some manner or degree; but unfortunately many people are bad ones and suffer harm in consequence. It is just the same in other matters. Even if we do not know the meaning of the name, we are all _athletes_ in some manner or degree. No one can climb a tree or get over a gate without being more or less an athlete. Nevertheless, he who wishes to do these actions really well, to have a strong muscular frame and thereby to secure good health and personal safety, as far as possible, should learn athletic exercises.”