PROPOSITIONS. 45 



the exact likeness of the substance in several qualities to 

 other pieces of substance which are undoubtedly of gold. 

 I must make a judgment of the colour, the specific 

 gravity, the hardness, sound, and chemical properties ; 

 and each of these judgments might be expressed in an 

 elementary proposition, 'the colour of this coin is the 

 colour of gold/ and so on. Even when we establish 

 the identity of a thing with itself under a different 

 name or aspect, it is by distinct judgments concerning 

 r single circumstances. To prove that the Homeric xa\K6g 

 is copper we must show the identity of each quality 

 recorded of x a ^ K v with a quality of copper. To establish 

 Deal as the landing-place of Caesar, every circumstance 

 must be shown to agree. If the modern Wroxeter is 

 the ancient Uriconium, there must be the like agreement 

 of all features of the country not subject to alteration by 

 time. 



All such identities may be expressed in the form A = B. 

 We may say 



Colour of Pacific Ocean = Colour of Atlantic Ocean. 

 Smell of rotten egg = Smell of hydrogen sulphide. 

 In these and similar propositions we assert identity of 

 single qualities or sensations. But in the same form 

 we may express identity of any group of qualities, as in 



^aA/co'? = Copper. 



Deal = Landing-place of Caesar. 



A multitude of propositions involving singular terms fall 

 into the same form, as in 



The Pole star = The slowest-moving star. 



Jupiter = The greatest of the planets. 



The ringed planet = The planet having seven satel- 

 lites. 



The Queen of England = The Queen of India. 



The number two = The even prime number. 



Honesty = The best policy. 



