In order to convince another of a truth which conflicts with an error he firmly holds, the first rule to be observed, is an easy and natural one: let the premisses come first, and the conclusion follow. Yet this rule is seldom observed, but reversed; for zeal, eagerness, and dogmatic positiveness urge us to proclaim the conclusion loudly and noisily against him who adheres to the opposed error. This easily makes him shy, and now he opposes his will to all reasons and premisses, knowing already to what conclusion they lead. Therefore we ought rather to keep the conclusion completely concealed, and only advance the premisses [pg 306] distinctly, fully, and in different lights. Indeed, if possible, we ought not to express the conclusion at all. It will come necessarily and regularly of its own accord into the reason of the hearers, and the conviction thus born in themselves will be all the more genuine, and will also be accompanied by self-esteem instead of shame. In difficult cases we may even assume the air of desiring to arrive at a quite opposite conclusion from that which we really have in view. An example of this is the famous speech of Antony in Shakspeare's “Julius Cæsar.”
In defending a thing many persons err by confidently advancing everything imaginable that can be said for it, mixing up together what is true, half true, and merely plausible. But the false is soon recognised, or at any rate felt, and throws suspicion also upon the cogent and true arguments which were brought forward along with it. Give then the true and weighty pure and alone, and beware of defending a truth with inadequate, and therefore, since they are set up as adequate, sophistical reasons; for the opponent upsets these, and thereby gains the appearance of having upset the truth itself which was supported by them, that is, he makes argumenta ad hominem hold good as argumenta ad rem. The Chinese go, perhaps, too far the other way, for they have the saying: “He who is eloquent and has a sharp tongue may always leave half of a sentence unspoken; and he who has right on his side may confidently yield three-tenths of his assertion.”
Chapter XII.[23] On The Doctrine Of Science.
From the analysis of the different functions of our intellect given in the whole of the preceding chapters, it is clear that for a correct use of it, either in a theoretical or a practical reference, the following conditions are demanded: (1.) The correct apprehension through perception of the real things taken into consideration, and of all their essential properties and relations, thus of all data. (2.) The construction of correct conceptions out of these; thus the connotation of those properties under correct abstractions, which now become the material of the subsequent thinking. (3.) The comparison of those conceptions both with the perceived object and among themselves, and with the rest of our store of conceptions, so that correct judgments, pertinent to the matter in hand, and fully comprehending and exhausting it, may proceed from them; thus the right estimation of the matter. (4.) The placing together or combination of those judgments as the premisses of syllogisms. This may be done very differently according to the choice and arrangement of the judgments, and yet the actual result of the whole operation primarily depends upon it. What is really of importance here is that from among so many possible combinations of those different judgments which have to do with the matter free deliberation should hit upon the very ones which serve the purpose and are decisive. But if in the first function, that is, in the apprehension through perception [pg 308] of the things and relations, any single essential point has been overlooked, the correctness of all the succeeding operations of the mind cannot prevent the result from being false; for there lie the data, the material of the whole investigation. Without the certainty that these are correctly and completely collected, one ought to abstain, in important matters, from any definite decision.
A conception is correct; a judgment is true; a body is real; and a relation is evident. A proposition of immediate certainty is an axiom. Only the fundamental principles of logic, and those of mathematics drawn a priori from intuition or perception, and finally also the law of causality, have immediate certainty. A proposition of indirect certainty is a maxim, and that by means of which it obtains its certainty is the proof. If immediate certainty is attributed to a proposition which has no such certainty, this is a petitio principii. A proposition which appeals directly to the empirical perception is an assertion: to confront it with such perception demands judgment. Empirical perception can primarily afford us only particular, not universal truths. Through manifold repetition and confirmation such truths indeed obtain a certain universality also, but it is only comparative and precarious, because it is still always open to attack. But if a proposition has absolute universality, the perception to which it appeals is not empirical but a priori. Thus Logic and Mathematics alone are absolutely certain sciences; but they really teach us only what we already knew beforehand. For they are merely explanations of that of which we are conscious a priori, the forms of our own knowledge, the one being concerned with the forms of thinking, the other with those of perceiving. Therefore we spin them entirely out of ourselves. All other scientific knowledge is empirical.
A proof proves too much if it extends to things or cases of which that which is to be proved clearly does not hold good; therefore it is refuted apagogically by these. The [pg 309] deductio ad absurdum properly consists in this, that we take a false assertion which has been made as the major proposition of a syllogism, then add to it a correct minor, and arrive at a conclusion which clearly contradicts facts of experience or unquestionable truths. But by some round-about way such a refutation must be possible of every false doctrine. For the defender of this will yet certainly recognise and admit some truth or other, and then the consequences of this, and on the other hand those of the false assertion, must be followed out until we arrive at two propositions which directly contradict each other. We find many examples in Plato of this beautiful artifice of genuine dialectic.
A correct hypothesis is nothing more than the true and complete expression of the present fact, which the originator of the hypothesis has intuitively apprehended in its real nature and inner connection. For it tells us only what really takes place here.
The opposition of the analytical and synthetical methods we find already indicated by Aristotle, yet perhaps first distinctly described by Proclus, who says quite correctly: “Μεθοδοι δε παραδιδονται; καλλιστη μεν ἡ δια της αναλυσεως επ᾽ αρχην ὁμολογουμενην αναγουσα το ζητουμενον; ἡν και Πλατων, ὡς φασι, Λαοδαμαντι παρεδωκεν. κ.τ.λ.” (Methodi traduntur sequentes: pulcherrima quidem ea, quæ per analysin quæsitum refert ad principium, de quo jam convenit; quam etiam Plato Laodamanti tradidisse dicitur.) “In Primum Euclidis Librum,” L. iii. Certainly the analytical method consists in referring what is given to an admitted principle; the synthetical method, on the contrary, in deduction from such a principle. They are therefore analogous to the επαγωγη and απαγωγη explained in chapter ix.; only the latter are not used to establish propositions, but always to overthrow them. The analytical method proceeds from the facts; the particular, to the principle or rule; the universal, or from the consequents to the reasons; the other conversely. Therefore it would [pg 310] be much more correct to call them the inductive and the deductive methods, for the customary names are unsuitable and do not fully express the things.