268 THE GRAMMAR OF SCIENCE 



atom themselves come to be. From our standpoint, they 

 are justified as conceptions if they enable us to resume 

 our perceptual experience. But as there are many who 

 will insist on projecting the conceptual into the pheno- 

 menal field, I will endeavour to answer the question by 

 suggestion. 



Suppose we had two opaque horizontal plane surfaces 

 placed close together, and containing between them water 

 in which lived a flat fish, say a flounder. Now it is clear 

 that the perceptions of our fish would be limited to motion 

 forwards or backwards, to right or to left, but vertically 

 upwards or downwards would be an imperceptible, and 

 therefore probably inconceivable, motion for him. Now 

 let us pass in conception to a limit unrealisable in per- 

 ception ; let us suppose our flounder to get flatter and 

 flatter, and the film of water thinner and thinner, as the 

 planes are pressed closer together. The motion of the 

 flounder and the motion of the water may then, for con- 

 ceptual purposes, be supposed to take place in one hori- 

 zontal plane. Now if we were to make a hole in one of 

 the planes and squirt water in, it is clear that our flounder 

 would experience new sense-impressions when he came 

 into the neighbourhood of the squirt. Indeed the pressure 

 produced by the flow of water might compel the flounder 

 to circumnavigate the squirt — that is, the squirt might be 

 for him hard and impenetrable. Such squirts, although 

 only water in motion, might form very material groups of 

 sense-impressions for our fish. If, however, he were told 

 that matter was formed of squirts, he would be quite un- 

 able to conceive where the squirting came from. It could 

 be from neither forwards nor backwards, neither from right 

 nor left, for it flows in in all these directions. The 

 flounder would presume we were quite mad did we suggest 

 that the water came vertically upwards or downwards ; 

 that there was another direction in space — " upward and 

 outward in the direction of his stomach," as the author of 

 Flatland^ felicitously expresses it. Could the flounder 



1 Flat land : a Romance of Many Dimensions, by A. Square. London, 

 1884. 



