Reason and Invention. 847 



lire, not on account of physical pain inflicted by the fire, but from ter- 

 ror of pain anticipated. Anticipation can arise only from memor}'. 

 They anticipate injuiy only because it has been experienced from the 

 same cause in the past either by themselves or some of their tribe. 

 Here is a definite idea of cause and effect. A savage man perceives 

 this relation of fire to the destruction and pain of his body, and his per- 

 ceptions go further, for he can produce fire by violently rubbing two dry 

 sticks together. He perceives the relation of cause and effect between 

 his exertion and fire. The modern civilized philosopher and chemist 

 has carried his observations still further, and will tell you that the heat 

 which sets the sticks on fire is a new form of the motion of rubbing, 

 and that the blaze is the result of the union of oxygen with the disin- 

 tegrated carbon of the sticks. The conclusions of the last observer do 

 not invalidate those of the former ones. They simply extend to relation- 

 ships not perceived by the former observers. The recognition of Cause 

 and Effect arises when we experience, several times in succession, a 

 group of sensations, always occurring together, which bear to each 

 other a constant relationship of antecedent and consequent. The repe- 

 tition of the experience gives sensations of uniformity and constancy, 

 and hence necessity, and these are involved in the recognition. It is 

 easy to fall into error when sensations of things not really related occur 

 together in our sensorium, and it is equally easy to miss such relation- 

 ships when the sensatiofns are separted a little from each other. Thus 

 every savage can perceive the connection between sunlight and the sun, 

 and moonlight and the moon, but further observation is required to con- 

 nect moonlight with the sun. 



The perception of cause and effect is by no means a peculiarly human 

 faculty, but it is a property of every animal brain ; the extent and 

 variety of the perceptions depending directly upon the size of the cere- 

 brum. As all our perceptions are founded upon sensations, it follows 

 that the final proofs of the truth of a conclusion of reason are derived 

 through the senses, and are in fact sensations. The onty guarantee we 

 can have that any sensation is a correct transcript of an external object, 

 is the supporting testimon}" of more sensations. A skillful painter can 

 represent a ball on canvas so that from a certain standpoint the eye may 

 be deceived into reporting it a ball. But if the point of view be 

 changed, or if the sense of touch be brought in to make the test, new 

 sensations are aroused which correct the first one. It is so in all reason- 

 ing. All demonstration consists finally in an appeal to the senses. It 

 may not always.be necessary to carry the appeal so far. It may be 

 sufficient to go only a& far as the memory of things. 



The science of geometry, for example, is founded upon a lot of ax- 

 ioms and postulates ; an axiom being defined as a self-evident truth, and 



