420 



OPERATIONS SUBSIDIARY TO INDUCTION. 



tions subsidiary to induction is claimed 

 by Observation. This is not, however, 

 the place to lay down rules for mak- 

 ing good observers ; nor is it within 

 the competence of Logic to do so, but 

 of the art of intellectual Education. 

 Our business with observation is only 

 in its connection with the appropriate 

 problem of Logic, the estimation of 

 evidence. We have to consider, not 

 how or what to observe, but under 

 what conditions observation is to be 

 relied on ; what is needful, in order 

 that the fact, supposed to be observed, 

 may safely be received as true. 



§ 2. The answer to this question is 

 very simple, at least in its first aspect. 

 The sole condition is, that what is 

 supposed to have been observed shall 

 really have been observed ; that it be 

 an observation, not an inference. For 

 in almost every act of our perceiving 

 faculties, observation and inference 

 are intimately blended. What we are 

 said to observe is usually a compound 

 result, of which one-tenth may be ob- 

 servation, and the remaining nine- 

 tenths inference. 



I affirm, for example, that I hear a 

 man's voice. This would pass, in com- 

 mon language, for a direct perception. 

 All, however, which is really percep- 

 tion, is that I hear a sound. That 

 the sound is a voice, and that voice 

 the voice of a man, are not percep- 

 tions but inferences. I affirm, again, 

 that I saw my brother at a certain 

 hour this morning. If any proposi- 

 tion concerning a matter of fact would 

 commonly be said to be known by the 

 direct testimony of the senses, this 

 surely would be so. The truth, how- 

 ever, is far otherwise. I only saw a 

 certain coloured surface ; or rather I 

 had the kind of visual sensations 

 which are usually produced by a 

 coloured surface ; and from these as 

 marks, known to be such by pre- 

 vious experience, I concluded that I 

 saw my brother. I might have had 

 sensations precisely similar when my 

 brother was not there. I might have 

 (Been eome other person so nearly re- 



sembling him in appearance as, at 

 the distance, and with the degree of 

 attention which I b«stowed, to be 

 mistaken for him. I might have 

 been asleep, and have dreamed that 

 I saw him ; or in a nervous state of 

 disorder, which brought his image be- 

 fore me in a waking hallucination. 

 In all these modes, many have been 

 led to believe that they saw persons 

 well known to them, who were dead 

 or far distant. If any of these sup- 

 positions had been true, the affirma- 

 tion that I saw my brother would 

 have been erroneous ; but whatever 

 was matter of direct perception, 

 namely, the visual sensations, would 

 have been real. The inference only 

 would have been ill grounded ; I 

 should have ascribed those sensations 

 to a wrong cause. 



Innumerable instances might be 

 given, and analysed in the same man- 

 ner, of what are vulgarly called errors 

 of sense. There are none of them 

 properly errors of sense ; they are erro- 

 neous inferences from sense. When 

 I look at a candle through a multi- 

 plying glass, I see what seems a dozen 

 candles instead of one : and if the real 

 circumstances of the case were skil- 

 fully disguised, I might suppose that 

 there were really that number ; there 

 would be what is called an optical 

 deception. In the kaleidoscope there 

 really is that deception : when I look 

 through the instrument, instead of 

 what is actually there, namely, a casual 

 arrangement of coloured fragments, 

 the appearance presented is that of 

 the same combination several times 

 repeated in symmetrical arrangement 

 round a point. The delusion is of 

 course effected by giving me the same 

 sensations which I should have had 

 if such a symmetrical combination 

 had really been presented to me. If 

 I cross two of my fingers, and bring 

 any small object, a marble, for in- 

 stance, into contact with both, at 

 points not usually touched simulta- 

 neously by one object, I can hardly, 

 if my eyes are shut, help believing 

 that there 9,vo two mfti'bles instead of 



