ANALYSIS OF SCIENTIFIC CONCEPTS 239 



the belief asserts. Derivative beliefs in this sense constantly 

 arise without any process of logical inference, merely by 

 association of ideas or some equally extra-logical process." x 

 Hence it is possible for a belief to be psychologically derived 

 but logically primitive, since it is not the result of any 

 logical deduction. "We naturally believe, for example, 

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

 when we turn our backs upon them. . . . The belief that 

 they persist is, in all men except a few philosophers, logically 

 primitive, but it is not psychologically primitive; psycholog- 

 ically, it arises only through our having seen those tables and 

 chairs, trees and mountains." 2 The basic problem then 

 becomes: "Can the existence of anything other than our 

 own hard data be inferred from the existence of those data," 3 

 i.e., can the existence of anything which is psychologically 

 derived be inferred from the existence of something which is 

 psychologically primitive? As applied to the field of physics 

 the problem is that of "bridging the gulf between the world 

 of physics and the world of sense." 4 The former reveals 

 " a set of indestructible entities which may be called particles, 

 moving relatively to each other in a single space and time" 5 

 while the latter reveals a mass of gross and changing objects, 

 located in private spaces and private times. The problem is, 

 then, "to show the kind of way in which, given a world with 

 the kind of properties that psychologists find in the world 

 of sense, it may be possible, by means of purely logical 

 constructions, to make it amenable to mathematical treat- 

 ment by defining series or classes of sense-data which can 

 be called respectively particles, points, and instants. If 

 such constructions are possible, then mathematical physics 

 is applicable to the real world, in spite of the fact that its 

 particles, points, and instants are not to be found among 

 actually existing entities." 6 The similarities between this 

 analysis and the threefold approach suggested above are 

 obvious. 



1 Ibid., p. 69. 3 Ibid., p. 73. 5 Ibid., p. 104. 



2 Ibid., p. 70. * Ibid., p. 101. 6 Ibid., p. 122. 



