86 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



tion of 'regularities and recurrents" which are noticeable 

 in this immediately given content. "We call these regular- 

 ities of experience laws of Nature." 1 But science does not 

 remain in this limited realm. "Broadly speaking the task 

 of physical science is to infer knowledge of external objects 

 from a set of signals passing along our nerves." 2 This 

 proves to be necessary because "it is the inexorable law of 

 our acquaintance with the external world that that which is 

 presented for knowing becomes transformed in the process 

 of knowing." 3 From this, the character of the knowing sit- 

 uation is clearly ascertainable. So far as immediate and 

 certain knowledge is concerned, we are limited to our own 

 individual sense experiences ; we can classify them and formu- 

 late the laws of their interrelationships. But on the basis 

 of this knowledge we may make — indeed, we must make — 

 inferences to an "external' world, since we apparently 

 know that these sense experiences are the results of acts of 

 transformation and cannot therefore afford reliable informa- 

 tion as to their causes. Our knowledge of an external world 

 is wholly inferential in character. 



If one examines the three theories of perception here 

 considered, viz., the common sense theory, positivism, and 

 subjectivism, he can recognize that each represents, in a 

 sense, an attempt to overcome the inadequacies of the 

 preceding. The common sense theory is unsuccessful be- 

 cause of two features: it makes all knowledge indirect and 

 thus denies the possibility of knowing an external world, 

 and it forbids the mind by its own creative acts to make 

 any contributions to knowledge. Positivism apparently 

 recognizes at least the first of these difficulties and attempts 

 to avoid it by supposing that knowledge is always direct. 

 There is reason to believe that this is an improvement on 

 the common sense position. But a new difficulty arises. 

 If knowledge is always direct, how is error possible? If 

 there is nothing which comes between the observer and the 

 object, and if observation is the passive response to the 



1 Ibid., p. 8. 2 Ibid., p. 6. 3 Ibid., p. 7. 



