ILLUSTRATIONS OF THE LOGIC OF SCIENCE. 297 



ways in which A B might be resolved into the sum of two accelera- 

 tions. 



After this tedious explanation, which I hope, in view of the ex- 

 traordinary interest of the conception of force, may not have exhaust- 

 ed the reader's patience, we are prepared at last to state the grand 

 fact which this conception embodies. This fact is that if the actual 

 changes of motion which the different particles of bodies experience 

 are each resolved in its appropriate way, each component accelera- 

 tion is precisely such as is prescribed by a certain law of Nature, 

 according to which bodies in the relative positions which the bod- 

 ies in question actually have at the moment, 1 always receive certain 

 accelerations, which, being compounded by geometrical addition, give 

 the acceleration which the body actually experiences. 



This is the only fact which the idea of force represents, and who- 

 ever will take the trouble clearly to apprehend what this fact is, per- 

 fectly comprehends what force is. Whether we ought to say that a 

 force is an acceleration, or that it causes an acceleration, is a mere 

 question of propriety of language, which has no more to do with our 

 real meaning than the difference between the French idiom "11 fait 

 froicV and its English equivalent "It is cold" Yet it is surprising 

 to see how this simple affair has muddled men's minds. In how many 

 profound treatises is not force spoken of as a " mysterious entity," 

 which seems to be only a way of confessing that the author despairs 

 of ever getting a clear notion of what the word means ! In a recent 

 admired work on " Analytic Mechanics " it is stated that we under- 

 stand precisely the effect of force, but what force itself is we do not 

 understand ! This is simply a self-contradiction. The idea which the 

 word force excites in our minds has no other function than to affect 

 our actions, and these actions can have no reference to force other- 

 wise than through its effects. Consequently, if we know what the 

 effects of force are, we are acquainted with every fact which is implied 

 in saying that a force exists, and there is nothing more to know. The 

 truth is, there is some vague notion afloat that a question may mean 

 something which the mind cannot conceive; and when some hair- 

 splitting philosophers have been confronted with the absurdity of 

 such a view, they have invented an empty distinction between posi- 

 tive and negative conceptions, in the attempt to give their non-idea 

 a form not obviously nonsensical. The nullity of it is sufficiently plain 

 from the considerations given a few pages back ; and, apart from 

 those considerations, the quibbling character of the distinction must 

 have struck every mind accustomed to real thinking. 



IV. 



Let us now approach the subject of logic, and consider a concep- 

 tion which particularly concerns it, that of reality. Taking clearness 



1 Possibly the velocities also have to be taken into account. 



