CHAPTER III. 



PROPOSITIONS. 



WE now proceed to consider the variety of forms of 

 propositions in which the truths of science must be 

 expressed. I shall endeavour to show that, however 

 diverse these forms may be, they all admit the application 

 of the one same principle of influence, that what is true 

 of one thing or circumstance is true of the like or same. 

 This principle holds true whatever be the kind or manner 

 of the likeness, provided proper regard be had to its 

 degree. Propositions may assert an identity of time, 

 space, manner, quantity, degree, or any other circumstance 

 in which things may agree or differ. 



We find an instance of a proposition concerning time 

 in the following : ' The year in which Newton was born, 

 was the year in which Galileo died.' This proposition 

 expresses an approximate identity of time between two 

 events ; hence whatever is true of the year in which 

 Galileo died is true of that in which Newton was born, 

 and vice versd. ' Tower Hill is the place where Raleigh 

 was executed' expresses an identity of place ; and what- 

 ever is true of the one spot is true of the spot otherwise 

 defined, but in reality the same. In ordinary language 

 we have many propositions obscurely expressing identities 

 of number, quantity, or degree. ' So many men, so many 

 minds/ is a proposition concerning number or an equa- 

 tion ; whatever is true of the number of men is true of 

 the number of minds, and vice versd. ' The density of 

 Mars is (nearly) the same as that of the Earth,' ' The force 



