80 SCIENTIFIC METHOD IN PHILOSOPHY 



objects ? And more generally, what are we to make of 

 the hypothetical sensations of touch which we associate 

 with untouched visible objects, which we know would be 

 verified if we chose, though in fact we do not verify 

 them ? Must not these be attributed to permanent 

 possession, by the objects, of the properties which touch 

 would reveal ? 



Let us consider the more general question first. 

 Experience has taught us that where we see certain kinds 

 of coloured surfaces we can, by touch, obtain certain 

 expected sensations of hardness or softness, tactile shape, 

 and so on. This leads us to believe that what is seen is 

 usually tangible, and that it has, whether we touch it or 

 not, the hardness or softness which we should expect to 

 feel if we touched it. But the mere fact that we are able 

 to infer what our tactile sensations would be shows that 

 it is not logically necessary to assume tactile qualities 

 before they are felt. All that is really known is that the 

 visual appearance in question, together with touch, will 

 lead to certain sensations, which can necessarily be 

 determined in terms of the visual appearance, since 

 otherwise they could not be inferred from it. 



We can now give a statement of the experienced facts 

 concerning the blue spectacles, which will supply an 

 interpretation of common-sense beliefs without assuming 

 anything beyond the existence of sensible objects at the 

 times when they are sensible. By experience of the 

 correlation of touch and sight sensations, we become able 

 to associate a certain place in touch-space with a certain 

 corresponding place in sight-space. Sometimes, namely 

 in the case of transparent things, we find that there is a 

 tangible object in a touch-place without there being any 

 visible object in the corresponding sight-place. But in 

 such a case as that of the blue spectacles, we find that 



