22 AN INTRODUCTION TO SCIENCE 



we know that force cannot be exhibited except through 

 matter. Light is emitted by a burning candle, sound by a 

 vibrating violin string. Therefore the ghost which emits 

 light and sound must be material. These difficulties do not 

 occur to the simple villager, because to him force is not 

 a reality. It is an attribute, not a thing. He can see no 

 difficulty in supposing that a spirit can create force. 



If we ask the more learned believer in ghosts the obvious 

 question Whence comes the force by which a ghost reveals 

 itself? he answers that the question is beside the mark. 

 Every part of the body has its representation in spirit, and 

 our spirit is capable of perceiving other spirits without the 

 intervention of the senses. ' ' No force passes from the ghost 

 to you," he assures us. It is undoubtedly a thinkable posi- 

 tion, so far as the body is concerned, but what about the 

 clothes? Do they acquire a "spirit" by contact with a 

 human being ? If they do not, how is it that the clothing of 

 the ghost makes itself sensible to our spirits ? Few chapters 

 in social history are more interesting than the evolution of 

 the ghost. It has steadily progressed in the wake truly a 

 long way in the wake of science. Who can tell what the 

 unexceptionable ghost of the twentieth century may be like ? 



Proficiency in science is shown by a masterly skill in 

 cross-examining nature ; and, as every lawyer knows, no 

 case is proved as long as any antagonistic fact, however 

 trivial, cannot be explained away. ' ' The seeker after truth 

 must himself be truthful, truthful with the truthfulness of 

 nature. . . . Unscientific man is often content with the 

 ' nearly ' and the ' almost. ' Nature never is. ' ' This was the 

 doctrine preached by Sir Michael Foster in his address at 

 Dover as President of the British Association. It is the first 

 principle of science. Mathematics neglects the infinitely 

 small. Common sense is content with an approximation to 

 the truth, trusting, quite justifiably in the hurry of business, 

 that much that it does not understand is capable of explana- 

 tion. Science recognises no negligible quantity. "You 



