FALLACIES OF OBSERVATION. 403 



describe any natural phenomenon. "The simplest 

 narrative" says Dugald Stewart*, " of the most 

 illiterate observer involves more or less of hypo- 

 thesis ; nay, in general, it will be found that, in pro- 

 portion to his ignorance, the greater is the number of 

 conjectural principles involved in his statements. A 

 village apothecary (and, if possible, in a still greater 

 degree, an experienced nurse) is seldom able to 

 describe the plainest case, without employing a phra- 

 seology of which every word is a theory ; whereas a 

 simple and genuine specification of the phenomena 

 which mark a particular disease ; a specification 

 unsophisticated by fancy, or by preconceived opi- 

 nions, may be regarded as unequivocal evidence of a 

 mind trained by long and successful study to the most 

 difficult of all arts, that of the faithful interpretation 

 of naturef." 



The universality of the confusion between percep- 

 tions and the inferences drawn from them, and the 

 rarity of the power to discriminate the one from the 

 other, ceases to surprise us when we consider that in 

 the far greater number of instances the actual percep- 





* Elements of the Philosophy of the Mind, vol. ii., ch. 4, sect. 5. 



t The following anecdote, related by Dr. Paris (Pharmacolog'ia y 

 pp. 76 70 is an amusing instance of an inference mistaken for a ! 

 direct perception. " Shortly after Sir Humphry Davy had suc- 

 ceeded in decomposing the fixed alkalies, a portion of potassium'' (a 

 substance so light as to swim upon water,) " was placed in the hand 

 of one of our most distinguished chemists, with a query as to its 

 nature. The philosopher observing its aspect and splendour did 

 not hesitate in pronouncing it to be metallic, and uniting at once 

 the idea of weight with that of metal, the evidence of his senses was 

 even insufficient to dissever ideas so inseparably associated in his 

 mind, and, balancing the specimen on his fingers, he exclaimed, ' it 

 is certainly metallic, and very ponderous? " He mistook his judgment 

 of the ponderosity of the substance for a sensation of it. 



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