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ONE of the best-known modes of progress in knowledge is that which has received the name of the reductio ad absurdum, or correction of the premiss : that is, the fundamental thought which is taken as the starting point, in any given case, being imperfect, false conclusions are rendered necessary; and by the casting aside of these conclusions a truer fundamental thought is brought in. In the following remarks I shall endeavour to show that the correction of the premiss is the mode in which both the intellectual and the moral Life of the human race advance.

I. In respect to the intellectual life, man's advance is from ignorance ; and from ignorance to knowledge (apart from direct instruction from without) there is no other path than through the correction of the premiss. This is the necessary form of the attainment of knowledge.

One or two qualifications, not at all affecting the proposition, need perhaps to be made : thus, (1) When the premiss has been corrected

If the reader will recall any ordinary mental process, he will perceive, that when, in any case, he is ignorant of any essential circumstance, the conclusions he draws will not be true. The omission of truth, if any process of reasoning takes place, necessarily involves us in error. A person, for example, not knowing the existence of steam, would necessarily suppose false powers in the things moved by it. A man not knowing the weight of the atmosphere, by which lighter bodies are raised, must attribute to a balloon a power of ‘rising' that it does not possess. Savages, not knowing eclipses, have inferred devouring monsters. It is impossible that reasoning, in ignorance, should have any other effect than that of leading us to erroneous conclusions. Nor is the case different, if instead of reasoning, or together with it, observation be employed. Observation, based upon assumptions that include too little, leads also necessarily to error. So chemists, formerly, observing with all exactness the effect of burning, but without knowing that oxygen unites with the burning body, and that part of it is carried off in invisible gas, thought that something which they called phlogiston was given off by bodies in burning. The things we can directly observe are, at the utmost, but parts; and we cannot put them truthfully together while the parts which we cannot directly observe are wanting. Now, in ordinary affairs, no one either doubts or complains of the law that if he does not know the facts he falls into erroneous conclusions. Reason would not exist if it were otherwise. And if we turn to wider spheres it is evidently as little desirable, and as little possible, that ignorance should not lead to error. It is by means of the error that the ignorance is banished; by means of the false conclusions the premiss is rendered more complete, for by them men are driven to seek a truer thought. On how grand a scale this method of learning has been carried out, it needs but slight acquaintance with science to perceive. All the ancient astronomy, before the discovery of the earth's motion, was one magnificent demonstration in this form ; ignorance of that one fact compelled it to be so.

in any particular case there lies open a course, more or less fruitful, of observation and reasoning upon the new premiss thus acquired, before there arises the need for a repetition of the process. (2) A certain knowledge we may be said to possess without any process of acquiring it at all; namely, the knowledge that we have certain sensations. (3) It may be held by some that there is also a certain further amount of

instinctive' knowledge possessed by man which is exempt from this law, not having to be acquired.

But it is needless to multiply instances. Absence of knowledge has for its inevitable fruit this result: that the right exercise of our faculties leads, at first, not to

true but to false conclusions. The only means whereby our progress to knowledge can be made harmonious is in frankly recognising and accepting this law of our Life. For, be it ever so well understood, if it be not consciously accepted in its application to every problem which Nature presents to us, we turn against ourselves the very powers by which we might advance.

Conceive a master carrying a class, in good faith and with a view to their own real discovery of the truth, through a reductio ad absuruum: we perceive all the pupils starting from a common false conviction (for ignorance always feels itself to be knowledge); then, as the master's good logic or good observation carried them to the false conclusion, inevitably the class would divide itself into two portions : one affirming the false conclusion because supported by sound reasoning, or clear evidence; the other feeling the conclusion to be false, and insisting therefore on finding some flaw in the demonstration. Strife and opposition would come, and an endeavour to wrest from one another that which each maintained; a strife which must continue until the meaning of the process was perceived, and the premiss corrected. The pupils would divide themselves into two sides, according as they felt most the validity of the process by which the

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