THE MIND'S EYE. 



3 11 



ity, prepossession, as well as other circumstances influence the result. 

 These illustrations show conclusively that seeing is not wholly an 

 objective matter depending upon what there is to be seen, but is 

 very considerably a subjective matter depending upon the eye that 

 sees. To the same observer a given arrangement of lines now ap- 

 pears as the representation of one object and now of another; and 



Fig. 17a. 



Fig. 176. 



Fig. 17. 



Figs. 17, 17a, and 176. — How many blocks are there in this pile? Six or seven ? Note the 

 change in arrangement of the blocks as they change in number from six to seven. This 

 change is illustrated in the text. Figs. 17a and 17b show the two phases of a group of ai.y 

 three of the blocks. The arrangement of a pyramid of six blocks seems the more stable 

 and is usually first suggested ; but hold the page inverted, and you will probably see the 

 alternate arrangement (with, however, the black surfaces still forming the tops). And 

 once knowing what to look for, you will very likely be able to see either arrangement, 

 whether the diagram be held inverted or not. This method of viewing the figures upside 

 down and in other positions is also suggested to bring out the changes indicated in Figs. 

 13, 13a, 136, and in Figs. 15, 15a, 156. 



from the same objective experience, especially in instances that de- 

 mand a somewhat complicated exercise of the senses, different ob- 

 servers derive very different impressions. 



ISTot only when the sense-impressions are ambiguous or defective, 

 but when they are vague — when the light is dim or the forms obscure 



