Fallacies to Avoid

Chapter III — Fallacies to Avoid

When a fact has been proved by clear-cut and justified reasoning, deductive or inductive, it is said to be demonstrated. When one (or more) of the premisses of an argument is not certainly true, but only probably so, the conclusion reached is not demonstrated but shown to be probable. When one (or more) of the premisses is certainly false, although it bears the attractive appearance of truth; or when the conclusion is not justified in view of the premisses, although it seems, at first sight, to be so; then the argument is called a sophistry or a fallacy. The conclusion of a fallacy may express a truth, and then the conclusion is called illogical; or it may express a falsehood, and then it is called erroneous, or simply an error.

This Chapter discusses some of the more commonly used fallacies. Its purpose is to equip the student for the ready recognition of unjustified reasoning and ordinary logical error, and to relieve him of the necessity of making a laborious analysis of every seemingly valid argument that he may be called upon to criticize.

The Chapter is not divided into Articles. It lists and discusses the following fallacies:

1. Equivocation
2. Composition and Division
3. Evading the Point
4. Begging the Question
5. False Cause

1. Equivocation

This fallacy employs equivocal or vague terms that cause the argument, when reduced to the form of a syllogism, to offend against the First Law: “Three terms there must be, neither more nor less.” Example:

A box is a wooden case A blow on the ear is a box Therefore, a blow on the ear is a wooden case.

This absurd example is a very obvious fallacy; but it is of profit to notice that it contains four terms, not three, and that the syllogism is therefore unjustified. More intriguing is the equivocation which comes from the use of vague words and ambiguous terms like: democracy, brotherhood, humanitarianism, materialism, optimism, pessimism, prosperity, progress, education, dogmatism, higher planes, contacts, values, higher life, broader vision, etc. The use of such terms as these is very common in our day, and many people employ them constantly who could not, under direst penalties, frame an adequate definition of any one of them. From this fact the student should take two points for practical guidance: 1) Never use vague terminology; use terms in a clear and precise sense, and define them when necessary; 2) Never allow an opponent to “get away” with a vague argument: make him define his terms.

An example of equivocation through the use of vague terms:

Prosperity promotes progress Active commerce is prosperity Therefore, active commerce promotes progress.

What is meant by progress? Does it mean the increase of wealth and power in the hands of those already wealthy and powerful? Does it mean the intellectual illumination of mankind? Does it mean the triumph of those who war against human justice and the dignity of the citizen as a man and the image of God? What does it mean? To one thousand men the term progress conveys a thousand shades of meaning, — nay more: it conveys to nine hundred of the thousand men a meaning somewhat constant, but variously shaded; and to the other hundred it conveys a meaning that is opposed to the more general and constant interpretation of the term. The same may be said of the term prosperity. Therefore, the syllogism here given is valueless unless its terms be accurately explained; as it stands it is a fallacy. And how many minds, even educated minds, are content with such fallacies! Content to accept them as evidences of truth, content to assimilate them as the embodiment of wisdom, content to make them the practical norms and principles of conduct, and even of life!

2. Composition and Division

This fallacy attributes a predicate to a qualified subject when that predicate is applicable to the subject only when unqualified; or it attributes a predicate to an unqualified subject when that predicate is applicable to the subject only when qualified. In other words, this fallacy compounds subject and qualifier in one, and then attributes a predicate which belongs to the subject alone without the qualifier (Fallacy of Composition); or it divides a subject from its qualifier, and then attributes a predicate which belongs to that subject only when compounded with its qualifier (Fallacy of Division).

Example:

Sinners cannot get to heaven St. Augustine was a sinner Therefore, St. Augustine could not get to heaven.

Here we have the Fallacy of Division. The subject to which the predicate “those who cannot get to heaven” really applies is “unconverted sinners.” The fallacy divides the subject “sinners” from its qualifier “unconverted,” and then applies a predicate only applicable when the subject is undivided. Supplying the lacking qualifier, we have:

Unconverted sinners cannot get to heaven St. Augustine was a (converted) sinner Therefore — (four terms in premisses; no conclusion possible)

A further example:

To make blind men see is to do a contradictory thing Our Lord made blind men see Therefore, Our Lord did a contradictory thing.

This is the Fallacy of Composition. The term blind men is properly kept in compounded sense in the major premiss, which means “blind men as such cannot see, and to say that they can remain blind and yet see is a contradiction.” But in the minor premiss, the term ought to be understood in divided sense, as “those whom the Lord caused to cease to be blind and to see.” Our fallacy, however, holds it compounded or composed. To controvert this fallacy, we point out the fact that blind men in the major premiss is compounded or composed, and the same term in the minor premiss is or ought to be divided; hence we see that the syllogism involves equivocation, presents four terms, and baulks the drawing of any conclusion.

The example given here is made obviously false so that the student may go whole-heartedly into the task of finding out where its point of fallacy lies. But there are thousands of intriguing arguments, — not obviously false but which involve the Fallacy of Composition or that of Division, — seen in books and heard in lecture-halls and university class-rooms every day and every hour. The student will do well to be on guard against this very deceiving fallacy. Let him find the point of fallacy in the following:

The Mosaic Law is abrogated The Ten Commandments are part of the Mosaic Law Therefore, the Ten Commandments are abrogated.

I will not join a Church whose members are rascals Many members of the Catholic Church are rascals Therefore, I will not join the Catholic Church.

3. Evading the Point

This is a fallacy which offers argument or proof for something other than the point at issue. An example of this fallacy is found in the arguments of those zealots who set out to prove that Catholics are idolatrous, and spend their entire effort in proving that images are not to be adored, — a matter in which every Catholic will thoroughly agree. Another example is found in the usual type of argument offered in defense of the hypothesis of evolution. When the evolutionist is asked: “How did human life come into being from lower life-forms?” he is very likely to reply: “Well, you see, it took ages and ages, aeons and aeons, for the process of development to unfold to that stage which we behold in human life. Lower life-forms gradually developed variations, these became fixed, and were transmitted, and after the lapse of millions of years there emerged new species of a higher type than the originals. And so the process has gradually worked up to human life.” This is the fallacy of Evading the Point. It amounts to this:

Inquirer: “How did you get here?” Traveller: “It took me a long time to arrive.”

Another example of this fallacy is found in the natural philosophy of those who explain the bodily universe by declaring it made up of atoms; and who, if pressed, explain the atoms by saying that they are made up of nucleus and electrons, and so on. This is Evading the Point at issue. One does not explain a body as such by saying that it is made up of smaller bodies. This may be true, but it is not the point at issue; the point is clearly raised in the question, “What is a body?” It is not answered by saying, “It is a thing made up of smaller bodies.” The small body presents the same problem as the large body of which it is a tiny part. All this is evident in the following dialogue:

Inquirer: “What is a board?” Pseudo-Scientist: “It is a thing made up of many grains of sawdust.” Inquirer: “But what is a grain of sawdust?” Pseudo-Scientist: “It is a small body composed of numerous tiny particles.” Inquirer: “But, hang it man! what are those particles?” Pseudo-Scientist: “Ah, you have no respect for science!”

The dialogue must be offered, of course, with an apology to true scientists. But true scientists are rarities; and pseudo-scientists are multitudinous, and they preach at us, and write at us, and shout at us from rostrum and stage and pressroom and even pulpit! The fallacy of Evading the Point is one of the most common, and one of the most deceiving sophistries of modern times. Many educated minds accept this fallacy as valid argument. The student must be on his guard against it, and, for his guidance, he should keep two principles ever in mind: 1) Be perfectly clear about the exact point at issue; 2) Hold the adversary strictly to that point; do not permit him to wander off and prove something else, — and then claim victory.

4. Begging the Question

This fallacy assumes as proved the very point at issue, and draws from it arguments to establish its own truth. Of course, the assumption is usually covert — otherwise, the fallacy would be open error. In its most evident form this fallacy is “the vicious circle,” a good name, for it involves reasoning in a ring, proving A by B, and B by A. Thus Descartes proved the existence of God by the testimony of our reason; and then he proved reason valid by the perfection of God, Who could not give us deceiving faculties!

Let the student consider the following and see if he can find in it the fallacy of Begging the Question:

“…we must assume natural selection to be the principle of the metamorphoses, because all other apparent principles of explanation fail us, and it is inconceivable that there should be another capable of explaining the adaptation of organisms without assuming the help of a principle of design.”

As a suggestion to the student, let it be said that the question here is the existence or non-existence of a designer of the universe, and particularly of life in its varied forms. We offer no apologies to the scientist here, for the quotation is from a controversial article by August Weismann, German biologist and zoologist of note, who died in 1914. (Cf. The Contemporary Review, Sept. 1893.)

5. False Cause

This fallacy presents as the cause of a fact what has merely preceded it or accompanied it. Thus the fall of the Roman Empire was attributed by the pagans (and by Gibbon!) to the rise of Christianity. This fallacy is often called, “Post hoc, ergo propter hoc,” that is, “After this, therefore because of this.”

Other fallacies, the names of which are self-explanatory, are: False Analogy, Defective Induction, Incomplete Enumeration, False Assumption.

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Summary of the Chapter

This Chapter has taught us to be on our guard against the more common forms of logical error. This lesson has a twofold value: it makes us careful in constructing our own arguments and reasonings, and it enables us to brand illogicality in the arguments of others. The Chapter contains valuable principles for the guidance of the student, notably in the paragraphs which deal with Equivocation and Evading the Point — two of the most common and, at the same time, most powerful enemies of correct thinking.