82 DISCOURSE ON THE STUD? 



as to compel us to acknowledge that one or other 

 must be wrong. For example, nothing at first can 

 seem a more rational, obvious, and incontrovertible 

 conclusion, than that the colour of an object is an 

 inherent quality, like its weight, hardness, &c. and 

 that to see the object, and see it of its oum colour, 

 when nothing intervenes between our eyes and it, 

 are one and the same thing. Yet this is only a 

 prejudice ; and that it is so, is shown by bringing for- 

 ward the same sense of vision which led to its adop- 

 tion, as evidence on the other side ; for, when the 

 differently coloured prismatic raysj are thrown, in a 

 dark room, in succession upon any object, whatever 

 be the colour we are in the habit of calling its own, 

 it will appear of the particular hue of the light which 

 falls upon it : a yellow paper, for instance, will ap- 

 pear scarlet when illuminated by red rays, yellow 

 when by yellow, green by green, and blue by blue 

 rays ; its own (so called) proper colour not in the least 

 degree mixing with that it so exhibits. 



(72.) To give one or two more examples of the 

 kind of illusion which the senses practise on us, or 

 rather which we practise on ourselves, by a mis- 

 interpretation of their evidence: the moon at its 

 rising and setting appears much larger than when 

 high up in the sky. This is, however, a mere erro- 

 neous judgment ; for when we come to measure its 

 diameter, so far from finding our conclusion borne 

 out by fact, we actually find it to measure materially 

 less. Here is eyesight opposed to eyesight, with the 

 advantage of deliberate measurement. In ventrilo- 

 quism we have the hearing at variance with all the 

 other senses, and especially with the sight, which is 



