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 | [_No Conclusion_]
the hating parent |
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.'
I.
What is universally believed | is true
-----------------------------+-------
The existence of God is not | _N. C._
universally believed
To establish the conclusion aimed at, it would be necessary to lay
down as precedent--'What is not universally believed is not true.'