140 THE DATA 0F PHILOSOPHY. 



accepted as unquestionable: leaving the assumption of 

 their unquestionableness to be justified by the results. 



§ 40. How is it to be justified by the results? As any 

 other assumption is justified — by ascertaining that all the 

 conclusions deducible from it, correspond with the facts as 

 directly observed — by showing the agreement between the 

 experiences it leads us to anticipate, and the actual ex- 

 periences. There is no mode of establishing the validity of 

 any belief, except that of showing its entire cpngruity with 

 all other beliefs. If we suppose that a mass which has a 

 certain colour and lustre is the substance called gold, how 

 do we proceed to prove the hypothesis that it is gold? We 

 represent to ourselves certain other impressions which gold 

 produces on us, and then observe whether, under the appro- 

 priate conditions, this particular mass produces on us such 

 impressions. We remember, as we say, that gold has a high 

 specific gravity; and if, on poising this substance on the 

 finger, we find that its weight is great considering its bulk, 

 we take the correspondence between the represented im- 

 pression and the presented impression as further evidence 

 that the substance is gold. In response to a demand for 

 more proof, we compare certain other ideal and real effects. 

 Knowing that gold, unlike most metals, is insoluble in 

 nitric acid, we imagine to ourselves a drop of nitric acid 

 placed on the surface of this yellow, glittering, heavy sub- 

 stance, without causing corrosion; and when, after so plac- 

 ing a drop of nitric acid, no effervescence or other change 

 follows, we hold this agreement between the anticipation 

 and the experience to be an additional reason for thinking 

 that the substance is gold. And if, similarly, the great 

 malleability possessed by gold we find to be paralleled by 

 the great malleability of this substance; if, like gold, it 

 fuses at about 2,000 deg. ; crystallizes in octahedrons; is dis- 

 solved by selenic acid; and, under all conditions, does what 

 gold does under such conditions; the conviction that it is 



