FIRST PRINCIPLES 21 



asserted that the ghost was perfectly punctual and regular in 

 its habits. Every night as the clock struck twelve it mounted 

 the creaking stairs, entered the haunted room, deposited its 

 pack on the floor (it was the ghost of a murdered pedlar), 

 and uttered its formula "Three stages more, and then 

 comes death ! ' ' Several Cambridge men, including the 

 writer, spent a solitary night in the room with the blood- 

 stained floor the blood was found on examination to be 

 soluble in benzol, but that is a scientific detail yet no ghost 

 appeared. Not that the villagers' belief in their ghost was 

 in the least shaken by what might be regarded as a base 

 refusal on its part to substantiate their story. They were not 

 even surprised at the disappointment of the seekers after 

 truth. "What was the use," they asked, "of sending men 

 from Cambridge to see a ghost? Why, they don't believe in 

 anything in Cambridge!" Ghosts only show themselves 

 to persons who are prejudiced in their favour, and at the 

 Universities such a pre-possession is uncommon it is to be 

 hoped. The credulity implied by the villagers' word 

 "believe" is not a scientific attitude of mind. 



Now, without for a moment admitting that a scientific 

 training deadens the senses to sights and sounds which the 

 unscientific can perceive, we assert that loyalty to science 

 compels us, whether we can or cannot see and hear the 

 ghost, to ask for an explanation of its power of rendering 

 itself visible and audible. Emission of light and production 

 of sound are exhibitions of force, and by the law of the 

 conservation of energy a law which cannot be called in 

 question force is never either created or lost. When it 

 appears to us as a new force, we know that it is pre-existing 

 force translated into a new form. The force set free on the 

 combustion of coal came from the sun as radiant heat, which 

 enabled plants to decompose carbonic acid into carbon and 

 oxygen. When coal is burnt the carbon and oxygen again 

 unite, and the force which the plants stored up is set free. 

 Whatever a ghost may be, it cannot create force. Further, 



