io AN INTRODUCTION TO SCIENCE 



mental picture which written descriptions had caused him 

 to draw. No one can convey in words to his hearer or 

 reader an accurate conception of any phenomenon, even 

 though he may have observed it himself, and the passing 

 of the description through a second mind throws the picture 

 still further out of focus. But it is not only in accuracy that 

 the mental picture based upon descriptions is inferior to 

 the picture formed from autoptic observation, but also in 

 proportion. All facts are equally true, and yet every in- 

 vestigator knows that certain things which he observes 

 influence his judgment more than others, so that when he 

 is formulating a hypothesis he takes care that it squares 

 with them. This perfect assurance of the indisputable 

 accuracy of one's observations is a sentiment difficult to 

 convey, and since in the higher branches of all subjects it 

 is necessary to trust to the repute of observers in various 

 special fields, it is of the greatest consequence that every 

 one who assumes the position of teacher should have had 

 such personal Experience of research as will enable him to 

 adjust the amount of credence which he gives to the reports 

 of other workers. The supreme value of first-hand knowl- 

 edge has been so much insisted upon of late years that 

 it seems hardly necessary to accentuate it, yet the clearest 

 definition of the aim of science is that it seeks to know 

 Nature by personal contact. 



From a personal intimacy with Nature results such a 

 quick understanding of her manifestations as to constitute 

 what in other spheres of thought would be termed intuition. 

 The process of induction from observations occurs so quickly 

 that the observer draws his conclusions as soon as he sees 

 the phenomena, and he is therefore able to foretell with an 

 accuracy which his ability to give the reasons for his opinion 

 would not justify what will happen next what will be the 

 result of certain novel combinations. Shall we call this 

 scientific imagination? The term is self-contradictory, yet 

 its use is in some degree justified by- the analog)' of art. 



