XXX—OF PARALLEL ARRANGEMENT
There is no fault of perversion, mutilation, or entanglement in the statement of an argument that we do not meet with in actual reasoning. Even in the writings of educated and honest thinkers it is rare to meet with an argument the parts of which are clearly distinguished by the author himself, and expressed so as to show the precise degree of force they ought to carry. Reasoning is still only a semi-conscious process directed by rule-of-thumb. We make certain statements and find they have a power of moving others, so we continue to make them. But whether the result is due to the rationality of the discourse or merely to the docility of the hearers, we do not know, and—so long as the desired result follows—we do not care to inquire.
For this state of things logicians are to a great extent responsible. They are uncritical imitators of the Greek philosophers, whose notions on dialectic were quite wrong. The Greeks and their medieval and modern followers have squandered attention on a mental process which is not reason, mistaking it for reason, so that practically there has never been a science of dialectic. However much reasoners may have wished to present their thoughts coherently, they have not been provided with a method or notation adapted to the purpose. With an instinctive sense of the futility of the Syllogism, they have ignored it completely. I cannot call to mind a single controversial work that has been presented in syllogistic form, nor do even trained logicians use it overtly in argument.[18] Yet if it were what it professes to be, it would be as natural and convenient to express our arguments in syllogism as it is to put down on paper a sum in arithmetic. We are, as regards the expression of reasoning, in the position of numerical thinkers before the invention of figures and the elaboration of arithmetical rules. We have to do all our arguments 'in our head,' and so we do them badly. We can seldom be sure of the correctness of our own reasonings, and we are constantly being misled by sophistry. Nothing indeed will enable us to reason well or to detect false reasoning on a subject of which we are entirely ignorant, but a large measure of protection would be afforded by the adoption of a uniform system of presenting arguments, by which all the assumptions they involve are rendered explicit.
One of the commonest omissions in argumentation is to take the precedent for granted. This is allowable when it is a fact universally known or believed. 'If you let the glass fall it will be broken,'—the omitted precedent is the known consequences of letting brittle things fall to the ground. 'Caius is a liar, therefore he is a coward'—presupposes that every liar is a coward.
This liberty of suppression is sometimes used sophistically. The tacit precedent is not universally known or accepted, but if it is questioned the sophist is ready with an exclamation of surprise or contempt at our supposed ignorance. Persons who are afraid of appearing singular in their beliefs are liable to be deceived by this trick.
'It frequently happens,' says Whately, 'in the case of a fallacy [of omitted precedent] that the hearers are left to the alternative of supplying either a premiss which is not true, or else one which does not prove the conclusion: e.g. if a man expatiates on the distress of the country, and thence argues that the government is tyrannical, we must suppose him to assume either that "every distressed country is under a tyranny," which is a manifest falsehood, or merely that "every country under a tyranny is distressed," which, however true, proves nothing, the Middle Term being undistributed.... Which are we to suppose the speaker meant us to understand? Surely just whichever each of his hearers might happen to prefer: some might assent to the false premiss; others allow the unsound syllogism; to the sophist himself it is indifferent, as long as they can be brought to admit the conclusion.'
We sometimes attempt to reason from Contrast instead of resemblance, with a confused notion that things which differ in some respects must differ also in others. 'Who spareth the rod hateth the child; the parent who loveth his child must therefore spare not the rod.' The fallacy of this becomes apparent when we complete the theorem in the parallel form.
| VI. | |
| The hating parent | spares the rod |
| The loving parent differs from the hating parent | [No Conclusion] |
The following has often been presented as a valid argument—'What is universally believed must be true; the belief in God's existence is not universal; it is therefore not true.'