THE PROPERTIES OF MATERIAL OBJECTS 339 



which reveal the qualities of things, it does not end with them. 

 They constitute but a minor part of it. The main portion of it 

 is reached through the discovery of relations, a process which 

 involves, not merely perception, but thought. Thus, through 

 thought we link together dissimilar impressions (tactile, visual, 

 etc.) in groups by recognizing their relations to one another, and 

 so, by referring our impressions to the qualities of external objects, 

 construct our notions of the latter. For example, we construct 

 the notion of a sheet of paper by thinking that it has certain 

 properties. Facility in linking together impressions (i.e. skill in 

 thinking, skill in perceiving relations) is laboriously acquired 

 during infancy ; but later, when the facility has become so great 

 that we accomplish the task without effort, we forget the initial 

 difficulty and are apt to suppose, with the old school-men, that the 

 thinking is performed through intuition. In this way, also, we 

 learn the relations between the various objects thus constructed 

 for example between the ink, the pen, the paper, the table, the 

 room, the house, the street, and so on. Here again the relations 

 are not all perceived at a glance, but are thought out by a 

 process that becomes more and more complicated, but more facile, 

 as experience multiplies, knowledge increases, and skill grows. 



570. I notice that, though the number of objects in nature 

 appears to me to be limitless, the number of the different kinds 

 of properties they possess is much smaller. Objects have pro- 

 perties in common, for which reason we are able to classify them. 

 I observe that some properties, for instance extension in space 

 and persistence in time, are possessed by all real things within my 

 experience. Indeed I cannot conceive a real thing that does not 

 possess them. Others, for instance definite and persistent shape, 

 colour, and weight that I can feel, are very common. Others, 

 such as certain colours, are rare. Yet others, such as a particular 

 shape or place (e.g. the precise shape and place in the universe of 

 my face at this moment), are possessed by one object only. 

 Though the number of the different kinds of properties which I 

 can perceive are limited, yet they are so numerous and may be 

 possessed by objects in such varying degrees and combinations 

 that an infinite variety of objects is thereby rendered possible. 

 Thus a beetle has some properties (e.g. extension and weight) that 

 are possessed by a house ; but, because some of his properties (e.g. 

 vitality) differ from those of the house in kind while others differ 

 in degree, the two objects are very different and therefore dis- 

 tinguishable. 



