350 NECESSARY TRUTH 



of a phenomenon are so fully and exactly known that not only 

 a phenomenon of this general character, but just this very 

 phenomenon, with exactly these details, and each in exactly this 

 amount, must follow from those conditions, and from those only, 

 then that phenomenon is fully explained." 1 But when we think 

 of necessary truth, we must do so in terms of that reality to which 

 our minds seem to testify. If we question the reality, we can 

 declare, " Fact I doubt : and law I doubt : and, therefore, necessity 

 I doubt." But, given the fact and law, then necessity is beyond 

 all doubt. 



587. When tracing cause and effect, we do not refer explicitly 

 to all the qualities of the objects we are considering. Every object 

 has many qualities. Thus iron has persistence in time, extension 

 in space, weight, colour, frangibility, ductility, hardness, and a 

 multitude of others. It could not become hot, it could not even be 

 an object for us, unless it had at least many of them, for example, 

 persistence and extension, yet we do not think or say that the 

 poker becomes hot because it has persistence and extension. 

 Many pokers are not hot ; even ice which cannot become hot has 

 persistence and extension. We refer especially to the quality in 

 iron, its temperature, which is changed by the fire, and the quality in 

 the fire which is concerned in the change. The last is termed the 

 cause, the change in the first is termed the effect. 



588. More than one quality may be concerned in a cause ; thus 

 both the momentum and the hardness of a bullet are concerned in 

 the effect produced when it strikes another body. More than one 

 quality may be concerned in an effect ; thus the position, shape, 

 and temperature of a piece of iron may be changed when it is 

 struck. Nevertheless, no matter how many of the qualities of an 

 object are concerned when it acts on or is acted on by another object, 

 in practice we think only of those which are especially concerned : 

 or indeed, only of those of with which we are especially concerned. 

 Of course, no cause or effect stands isolated in the external world ; 

 we merely isolate it in thought. In reality it is connected not with 

 a chain, but with a circle of cause and effect. Thus a bullet, on 

 which certain properties were conferred during manufacture, flies 

 because it is impelled by the explosion of powder, ignited by a 

 spark in a gun, which was fired because a man, who was present 

 through a concatenation of circumstances that reaches back 

 through eternity, pulled a trigger because he was made angry by 

 certain events, and so on. Yet we say only that the one man was 



1 Welton, Manual of Logic, vol. ii. p. 188. 



