THE PERCEPTION OF SIGHT. 269 



than those which are perfectly apprehended. When more than 

 one interpretation is possible, we usually waver involuntarily 

 between them; but it is possible to end this uncertainty by 

 bringing the idea of any of the possible interpretations we 

 choose as vividly as possible before the mind by a conscious 

 effort of the will. 



These illusions obviously depend upon mental processes 

 which may be described as false inductions. But there are, no 

 doubt, judgments which do not depend upon our consciously 

 thinking over former observations of the same kind, and ex- 

 amining whether they justify the conclusion which we form. 

 I have, therefore, named these ' unconscious judgments ; ' and 

 this term, thoiigh accepted by other supporters of the Empirical 

 Theory, has excited much opposition, because, according to 

 generally-accepted psychological doctrines, a. judgment, or logical 

 conclusion, is the culminating point of the conscious operations 

 of the mind. But the judgments which play so great a part in 

 the perceptions we derive from our senses cannot be expressed 

 in the ordinary form of logically analysed conclusions, and it is 

 necessary to deviate somewhat from the beaten paths of psycho- 

 logical analysis in order to convince ourselves that we really 

 have here the same kind of mental operation as that involved 

 in conclusions usually recognised as such. There appears to 

 me to be in reality only a superficial difference between the 

 ' conclusions ' of logicians and those inductive conclusions of 

 which we recognise the result in the conceptions we gain of the 

 outer world through our sensations. The difference chiefly 

 depends upon the former conclusions being capable of expression 

 in words, while the latter are not ; because, instead of words, 

 they only deal with sensations and the memory of sensations. 

 Indeed, it is just the impossibility of describing sensations, 

 whether actual or remembered, in words, which makes it so 

 difficult to discuss this department of psychology at all. 



Besides the knowledge which has to do with Notions, and 

 is, therefore, capable of expression in words, there is another 

 department of our mental operations, which may be described 

 as knowledge of the relations of those impressions on the senses 



