70 SCIENTIFIC METHOD IN PHILOSOPHY 



they can on reflection be deduced by a logical process 

 from beliefs which are also psychologically primitive, our 

 confidence in their truth tends to diminish the more we 

 think about them. We naturally believe, for example, 

 that tables and chairs, trees and mountains, are still there 

 when we turn our backs upon them. I do not wish for 

 a moment to maintain that this is certainly not the case, 

 but 1 do maintain that the question whether it is the case 

 is not to be settled ofT-hand on any supposed ground of 

 obviousness. The belief that they persist is, in all men 

 except a few philosophers, logically primitive, but it is 

 not psychologically primitive ; psychologically, it arises 

 only through our having seen those tables and chairs, 

 trees and mountains. As soon as the question is seriously 

 raised whether, because we have seen them, we have a 

 right to suppose that they are there still, we feel that 

 some kind of argument must be produced, and that if 

 none is forthcoming, our belief can be no more than a 

 pious opinion. We do not feel this as regards the 

 immediate objects of sense : there they are, and as far 

 as their momentary existence is concerned, no further 

 argument is required. There is accordingly more need 

 of justifying our psychologically derivative beliefs than 

 of justifying those that are primitive. 



We are thus led to a somewhat vague distinction 

 between what we may call " hard ' data and " soft ' 

 data. This distinction is a matter of degree, and must 

 not be pressed ; but if not taken too seriously it may help 

 to make the situation clear. I mean by " hard " data those 

 which resist the solvent influence of critical reflection, 

 and by " soft ' data those which, under the operation 

 of this process, become to our minds more or less 

 doubtful. The hardest of hard data are of two sorts : 

 the particular facts of sense, and the general truths of 



