Logical fallacy

“ Bulwer, in remarking that error is a view of some facts instead of a survey of all, indicated the key to logical fallacy. Error lies principally in defective premises. Sophistry in science is referable to incomplete analysis of nature, of systems—to artificial arrangements—to supposing qualities, to assuming principles, to false inductions from imperfect demonstration. ”

“ A fallacy is a sophism, a logical artifice, a deceitful or false appearance; while specious means having the appearance of truth, plausible. Hence we see that the very essence of a fallacy is its speciousness. We may very properly say that a fallacy is more or less specious, but we can not properly say that a fallacy is specious, since without speciousness we can have no fallacies. ”

“ False ideas are held as true concerning all sorts of current problems—notions that take possession of men’s minds without logical reflection. The fallacy of confounding sequence with cause is almost universal. All kinds of subjective and objective duties suffer from illogical minds. ”

“ There is an obvious fallacy in the term 'all': like some other words, 'both,' 'odd,' 'even,' it is ambiguous, and even in abstract argument becomes a source of logical puzzles. That all persons call the same thing mine in the sense in which each does so may be a fine thing, but it is impracticable ”

“ The worthlessness of this sheer accumulation of realities, its total irrelevancy, the lack of any way of judging the significance of the accumulations, are good proofs of the fallacy of any theory which ascribes objective logical content to facts wholly apart from the needs and possibilities of a situation. ”

“ Fallacious Conclusion is in effect an unwarranted or irrelevant assumption of a logical conclusion. There are many forms of this fallacy among which are the following:
Shifting ground, which consists in the pretence of proving one thing while in reality merely a similar or related thing is being proved. In this class is the argument that because a man is profane he must necessarily be dishonest; or that because a man denies the inspiration of the Scriptures he must be an atheist. ”

“ But the theory, by which I have defined Metaphysical Ethics, is not that Metaphysics has a logical bearing upon the question involved in practical Ethics 'What effects will my action produce?,' but that it has such a bearing upon the fundamental ethical question, 'What is good in itself?.' This theory has been refuted by the proof, in Chap. I, that the naturalistic fallacy is a fallacy ”

“ About a hundred young women students, mostly college Juniors, were asked to introspect the impression produced upon them by a set of logical fallacies. In the original plan six of these faulty arguments were used, the design being to have two specimens of each of the three types of formal fallacy: illicit major, illicit minor, and undistributed middle ”

“ Facts gained from research in a library are easiest to verify, and other methods of gathering facts must often be re-verified through library research. Logical and emotional weaknesses of arguments can often be recognized by the use of certain fallacy recognition checklists. [6] The most widely used of the fallacies is the over or under generalization: everyone (all, without exception, none, never, no one) rode a bicycle when only two years old. [7]
* * * * *
The more common persuasive fallacies are:
LOGIC FALLACIES.
1. ”

“ Since every case where a conclusion which can only be proved from certain premises is used for the proof of those premises, is a case of _petitio principii_, that fallacy includes a very great proportion of all incorrect reasoning. It is necessary, for completing our view of the fallacy, to exemplify some of the disguises under which it is accustomed to mask itself, and to escape exposure. ”

“ But, in all except the most eminently philosophical minds, it is infected with precisely the same kind of fallacy as that is. For we must remember that even this other and better generalization, the progressive change in the condition of the human species, is, after all, but an empirical law ”

“ In this way all deeply-rooted opinions and feelings are enabled to create apparent demonstrations of their truth and reasonableness, as it were, out of their own substance.
The other form of the fallacy: Things which we can not think of together can not exist together—including as one of its branches, that what we can not think of as existing can not exist at all—may thus be briefly expressed: Whatever is inconceivable must be false. ”

“ Passing from physics to metaphysics, we may notice among the most remarkable fruits of this a priori fallacy two closely analogous theories, employed in ancient and modern times to bridge over the chasm between the world of mind and that of matter; the species sensibiles of the Epicureans, and the modern doctrine of perception by means of ideas. These theories are indeed, probably, indebted for their existence not solely to the fallacy in question, but to that fallacy combined with another natural prejudice already adverted to, that a thing can not act where it is not. ”

“ When a man confuses two natural objects with one another, defining the one by the other, if for instance, he confuses himself, who is one natural object, with ‘pleased’ or with ‘pleasure’ which are others, then there is no reason to call the fallacy naturalistic. ”

“ Arguments which are condemned by the vicious-circle principle will be called ‘vicious-circle fallacies.’ Such arguments, in certain circumstances, may lead to contradictions, but it often happens that the conclusions to which they lead are in fact true, though the arguments are fallacious. Take, for example, the law of excluded middle in the form ‘all propositions are true or false.’ If from this law we argue that, because the law of excluded middle is a proposition, [Pg 80] therefore the law of excluded middle is true or false, we incur a vicious-circle fallacy. ”

“ Conformably to what we have before remarked to be of frequent occurrence, this fallacy might without much impropriety have been placed in a different class, among Fallacies of Generalization: for experience does afford a certain degree of countenance to the assumption. The cause does, in very many cases, resemble its effect; like produces like. ”

“ Every species is vague, every term goes cloudy at its edges; and so in my way of thinking, relentless logic is only another name for a stupidity—for a sort of intellectual pigheadedness. If you push a philosophical or metaphysical inquiry through a series of valid syllogisms—never committing any generally recognised fallacy—you nevertheless leave behind you at each step a certain rubbing and marginal loss of objective truth, and you get deflections that are difficult to trace at each phase in the process. ”

“ If he is convinced of its character, he must either have grounds for that conviction or not. If he has grounds, let him examine them, draw them out, try if they are valid, and then the fallacy will stand exposed. If he has no grounds for suspecting a fallacy, what an irrational conclusion he confesses himself to have arrived at! ”

“ By a fallacy is meant a piece of reasoning which appears to establish a conclusion without really doing so. The term applies both to the legitimate deduction of a conclusion from false premisses and to the illegitimate deduction of a conclusion from any premisses. There are errors incidental to conception and judgement, which might well be brought under the name; but the fallacies with which we shall concern ourselves are confined to errors connected with inference. ”

“ I am indeed disposed to think that the fallacy now under consideration has been the cause of two-thirds of the bad philosophy, and especially of the bad metaphysics, which the human mind has never ceased to produce. Our general ideas contain nothing but what has been put into them, either by our passive experience, or by our active habits of thought ”

“ A negative use of this fallacy is very common. Some general doctrine, such as Positivism, Transcendentalism, Utilitarianism, or Darwinism, is held in common by a group of men; who, however, all judge independently, and therefore are likely to differ in details. An opponent exhibits their differences of opinion, and thereupon pretends to have refuted the theory they agree in supporting. This is an argumentum ad scholam, and pushes too far the [Pg 400] demand for consistency. ”

“ But this very fact points to causes of error so much more dangerous than the mere length of the process, as quite to vitiate the doctrine that the "test of the relative validities of conflicting conclusions" is the number of times the fundamental postulate is involved. On the contrary, the subjects on which the trains of reasoning are longest, and the assumption, therefore, oftenest repeated, are in general those which are best fortified against the really formidable causes of fallacy ”

“ If a dilemma is correct in form, the conclusion of course rigorously follows: but a material fallacy often underlies this form of argument in the tacit assumption that the alternatives offered in the minor constitute an exhaustive division. ”

“ This reasoning I conceive to be entirely fallacious, as indeed Dr. Brown, in his treatise on Cause and Effect, has shown with great acuteness and justness of thought. We have before remarked, that almost every fallacy may be referred to different genera by different modes of filling up the suppressed steps; and this particular one may, at our option, be brought under petitio principii. It supposes that nothing can be a “sufficient reason” for a body’s moving in one particular direction, except some external force. But this is the very thing to be proved. Why not some internal force? ”

“ And he proceeds to say, that independently of the love of the marvellous, or any other bias in the inclinations, there is a natural tendency in the intellect itself to this kind of fallacy; since the mind is more moved by affirmative instances, though negative ones are of most use in philosophy ”

“ Whately's logic is, of course, applied here—it is true in mood and figure, and yet the argument is fallacious. A fallacy is defined as 'an ingenious mixture of truth and falsehood, so entangled as to be intimately blended—that the falsehood is, in chemical phrase, held in solution: one drop of sound logic is that test which immediately disunites them, makes the foreign substance visible, and precipitates it to the bottom.'* But whence is to come 'this drop of sound logic?' Not from the Doctor's Elements, they have sent forth the fallacy. ”

“ Logicians are agreed that single ideas, thoughts viewed apart from judgments, are neither true nor false. Only a judgment can be false. And if a reasoning process is said to be false, the real error lies still in an actual or suppressed assertion. A fallacy is a false assertion that a certain conclusion follows from certain premises. Error is therefore generally defined as a judgment that does not agree with its object. In the erroneous judgment, subject and predicate are so combined as, in the object, the corresponding elements are not combined. ”

“ The former would be ranked, in our distribution, among fallacies of generalization, the latter among those of ratiocination. "Which are we to suppose the speaker meant us to understand? Surely" (if he understood himself) "just whichever each of his hearers might happen to prefer: some might assent to the false premise; others allow the unsound syllogism."
Almost all fallacies, therefore, might in strictness be brought under our fifth class, Fallacies of Confusion. A fallacy can seldom be absolutely referred to any of the other classes ”

“ For every property, therefore, in facts, or in our mode of considering facts, which leads us to believe that they are habitually conjoined when they are not, or that they are not when in reality they are, there is a corresponding kind of Fallacy; and an enumeration of fallacies would consist in a specification of those properties in facts, and those peculiarities in our mode of considering them, which give rise to this erroneous opinion. ”

“ Precisely the same error which leads them to suppose that there must exist a supersensible Reality, leads them to commit the naturalistic fallacy with regard to the meaning of ‘good.’ Every truth, they think, must mean somehow that something exists; and since, unlike the empiricists, they recognise some truths which do not mean which do not mean that anything exists here and now, these they think must mean that something exists not here and now. ”

“ To understand the wrong ways of reasoning is to be on guard against them. By guarding against them we tend to eliminate them from our thought processes. If we eliminate the false we have the true left in its place. Therefore we recommend the weeding of the logical garden of the common fallacies, to the end that the flowers of pure reason may flourish in their stead. Accordingly, we think it well to call your attention in the next chapter to the more common fallacies, and the reason of their falsity. ”

“ Fallacies in language, because they result from permitting more than one interpretation, may be also denominated fallacies of equivocation.
(1) Ambiguous middle is the fallacy of giving to the middle term a double meaning.
The fallacy of four terms, as the name signifies, exists when the argument has four terms in both form and meaning. Ambiguous middle is a matter of four terms in meaning but only three in form.
(2) The fallacy of amphibology is committed when the given proposition conveys more than one meaning. ”

“ Suppose another person proceed on the same principle, he must infer, that his future condition will be a most painful and unfortunate one, simply because his present condition is so. There is, then, a self-evident and a dangerous fallacy in the proposition which allows two persons to draw from it such opposite inferences, the one for, and the other against himself, and without any reference to personal conduct or character. ”