138 SCIENCE AND METHOD. 



far young people who have received a secondary 

 education are from applying the mechanical laws 

 they have been taught to the real world. It is not 

 only that they are incapable of doing so, but they 

 do not even think of it. For them the world of 

 science and that of reality are shut off in water-tight 

 compartments. It is not uncommon to see a well- 

 dressed man, probably a university man, sitting in 

 a carriage and imagining that he is helping it on by 

 pushing on the dash-board, and that in disregard of 

 the principle of action and reaction. 



If we try to analyze the state of mind of our pupils, 

 this will surprise us less. What is for them the true 

 definition of force ? Not the one they repeat, but the 

 one that is hidden away in a corner of their intellect, 

 and from thence directs it all. This is their definition: 

 Forces are arrows that parallelograms are made of; 

 these arrows are imaginary things that have nothing 

 to do with anything that exists in nature. This would 

 not happen if they were shown forces in reality before 

 having them represented by arrows. 



How are we to define force ? If we want a logical 

 definition, there is no good one, as I think I have 

 shown satisfactorily elsewhere. There is the anthro- 

 pomorphic definition, the sensation of muscular effort ; 

 but this is really too crude, and we cannot extract 

 anything useful from it. 



This is the course we ought to pursue. First, in 

 order to impart a knowledge of the genus force, we 

 must show, one after the other, all the species of this 

 genus. They are very numerous and of great variety. 

 There is the pressure of liquids on the sides of the 

 vessels in which they are contained, the tension of 



