Ch. 7
Of the use of the forms of right reasoning.
It is not understood by most persons that the proper
use of inferences and hypotheses and interrogations, and logical forms generally, has any relation to
the duties of life. In every matter of action the question is, how a wise and good man may come honestly
and consistently out of it. We must admit, therefore,
either that the wise man will not engage in difficult
problems or that, if he does, he will not think it
worth his care to deal with them thoroughly; or if we
allow neither of these alternatives, it is necessary to
confess that some examination ought to be made of
those points on which the solution of these problems
chiefly depends. For what is reasoning? To lay
down true positions, to reject false ones, and to suspend the judgment in doubtful ones. Is it enough,
then, to have learned merely this? It is enough, say
you. Is it enough, then, for him who would not commit any mistake in the use of money, merely to have
heard that we are to receive the good pieces, and to
reject the bad? This is not enough. What must be
added besides? That skill which tries and distinguishes what pieces are good, what bad. Therefore,
in reasoning too, the definition just given is not
enough; but it is necessary that we should be able to
prove and distinguish between the true and the false
and the doubtful. This is clear.
And what further is attempted in reasoning? To
admit the logical consequence of whatever you have
properly granted. Well, and is it enough merely to
know this necessity? It is not; but we must learn
how it happens that such a thing is the consequence
of such another, and when one thing follows from one
premise, and when from many premises. Is it not
moreover necessary that he who would acquit himself
skilfully in reasoning should both himself demonstrate
whatever he asserts and be able to comprehend the
demonstrations of others, and not be deceived by such
as use sophistry as if they were reasoning fairly?
Hence arises the use and practice of logical forms;
and it appears to be indispensable.
But it may possibly happen that from the premises
which we have honestly granted there arises some
consequence which, though false in itself, is nevertheless a fair inference. What then ought I to do? To
admit a falsehood? Impossible. To take back my
concessions? But this will not be allowed. Or assert that the consequence does not fairly follow from
the premises? Nor is even this practicable. What
then, is to be done in the case? Is it not this? As
the having once borrowed money is not enough to
make a person a debtor, unless he still continues to
owe money and has not paid it, so the having
granted the premises is not enough to make it necessary to grant the inference, unless we continue our
concessions. If the premises continue to the end
such as they were when the concessions were made, it
is absolutely necessary to continue the concessions,
and to admit what follows from them. But if the
premises do not continue such as they were when the
concession was made, it is absolutely necessary to revoke the concession, and refuse to accept the inference. For this inference is no consequence of ours,
nor belongs to us, when we have revoked the concession of the premises. We ought then thoroughly to
consider our premises and their different aspects, on
which any one, by laying hold, - either on the question itself or on the answer, or on the inference, or
elsewhere, -may embarrass the unthinking who did
not foresee the result. So that in this way we may not
be led into any unbecoming or confused position.
The same thing is to be observed in hypotheses and
hypothetical arguments. For it is sometimes necessary to require some hypothesis to be granted, as a
kind of step to the rest of the argument. Is every
given hypothesis, then, to be granted, or not every
one? and if not every one, which? And is he who has
granted an hypothesis forever to abide by it ! Or is
he sometimes to revoke it, and admit only conse-
quences, but not to admit contradictions? Ay, but a
person may say, on your admitting a possible hypothesis, "I will drive you upon an impossibility." With
such a one as this, shall the wise man never engage,
but avoid all argument and conversation with him?
And yet who beside the wise man is capable of treating an argument, or who beside is sagacious in reasoning, and incapable of being deceived and imposed on
by sophistry? Or will he indeed engage, but without
regarding whether he behaves rashly and heedlessly in
the argument? Yet how, then, can he be wise, as we
are supposing him? and without some such exercise
and preparation, how can he hold his own? If this
could be shown, then indeed all these forms of reasoning would be superfluous and absurd, and unconnected with our idea of the virtuous man.
Why, then, are we still indolent, and slothful, and
sluggish, seeking pretences of avoiding labor? Shall
we not be watchful to render reason itself accurate?
"But suppose, after all, I should make a mistake in
these points, - it is not as if I had killed my father."
O slavish man, in this case you had no father to kill.
but the only fault that you could commit in this instance, you have committed. This very thing I myself said
to Rufus when he reproved me for not finding the weak point in some syllogism. "Why," said
I, "have I burnt the capitol then?" "Slave !" answered he, "was the thing here involved the capitol?
Or are there no other faults but burning the capitol, or
killing a father?" And is it no fault to treat rashly,
and vainly, and heedlessly, the things which pass
before our eyes, - not to comprehend a reason, nor a
demonstration, nor a sophism; nor, in short, to see
what is strong in reasoning and what is weak? Is
there nothing wrong in this?